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Mercury’s（ ）is so much greater than the Earth’s that it completes more than four revolutions around the Sun in the time it takes the Earth to complete one.
A.velocity
B.orbit
C.weight
D.diameter
B.orbit
C.weight
D.diameter
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参考解析
解析：A选项意为“速度，速率”；B选项意为“轨道，活动范围”；C选项意为“重量，重要性，影响力”；D选项意为“直径，（透镜等的）倍率”。根据题意答案为A。
更多 “Mercury’s（ ）is so much greater than the Earth’s that it completes more than four revolutions around the Sun in the time it takes the Earth to complete one.A.velocity B.orbit C.weight D.diameter” 相关考题
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AWhen you look at the sky at night，the moon looks bigger than the stars． In fact，the moon is much smaller than the stars．It is much smaller than the earth． But the moon is much closer to us than any star． That is why it looks so big． If you hold a coin close．to your eye，it looks big．If you look at it across the room，it looks small．The moon moves around the earth． It makes one trip in about four weeks． The moon looks flat(扁的)to us． But it is a round ball，like the earth．People once thought the moon had fire(火) on it． They thought the fire made it bright．Now we know the moon is like a mirror( 镜子 )． It gets its light from the sun Our sunlight comes from the sun，too: What is the sun? The sun is star． The stars we can see have their own light． There are many big stars we can-t see． Their light has burned out． Others are still bright，but they are so far away that we can-t see them． The sun looks bigger and much brighter than other stars because it is the nearest of all stars． The sun and the other stars we see are very hot，but the air around us saves us from(使------免于) the heat(热量) of the sun．The sun gives us light and warmth．It makes plants grow and leaves turn green． It makes life possible on our earth．It is a life-giving star．( )21． The moon looks bigger because__________ ．A． some stars are smaller than itB．it is between the sun and the earthC．it is the closest to the earthD．it is very bright
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22．It takes__________ for the moon to go around the earthA． more than a weekB． nearly a monthC． half a yearD． more than a year
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Text 2 To understand how astrology works, we should first take a quick look at the sky. Although the stars are at enormous distances, they do indeed give the impression of being affixed to the inner surface of a great hollow sphere surrounding the earth. Ancient people, in fact, literally believed in the existence of such a celestial sphere. As the earth spins on its axis, the celestial sphere appears to turn about us each day, pivoting at points on a line with the earth's axis of rotation. This daily turning of the sphere carries the stars around the sky, causing most of them to rise and set, but they, and constellations they define, maintains fixed patterns on the sphere, just as the continent of Australian maintains its shape on a spinning globe of the earth. Thus the stars were called fixed stars.The motion of the sun along the ecliptic is, of course, merely a reflection of the revolution of the earth around the sun, but the ancients believed the earth was fixed and the sun had an independent motion of its own, eastward among the stars. The glare of sunlight hides the stars in daytime, but the ancients were aware that the stars were up there even at night, and the slow eastward motion of the sun around the sky, at the rate of about thirty degrees each month, caused different stars to be visible at night at different times of the year.The moon, revolving around the earth each month, also has an independent motion in the sky. The moon, however, changes its position relatively rapidly. Although it appears to rise and set each day, as does nearly everything else in the sky, we can see the moon changing position during as short an interval as an hour or so. The moon's path around the earth lies nearly in the same plane as the earth's path around the sun, so the moon is never seen very far from the ecliptic in the sky. There are five other objects visible to the naked eye that also appear to move in respect to the fixed background of stars on the celestial sphere. These are the planets Mercury, Venus, Mars, Jupiter, and the Saturn. All of them revolve around the sun in nearly the same plane as the earth does, so they, like the moon, always appear near the ecliptic. Because we see the planets from the moving earth, however, they behave in a complicated way, with their apparent motions on the celestial sphere reflection both their own independent motions around the sun and our motion as well.第26题：The ancient people believed that ________.[A] the earth was spinning on the axis of the sky[B] the sky was a hollow sphere spinning around the earth[C] the patterns of stars on the sky would never change[D] the stars around the sky were not stationary
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It is stated in astrology that ________.[A] the sun is so distant from us that it was hard to follow its motion[B] the sun was moving westward around the sky[C] the motion of the sun is at the rate of about thirty degrees every week[D] the motion of the sun is similar to the revolution of the earth around the sun
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All the other five planets ________.[A] always appear near the path of the sun[B] are moving in a way more complicated than the earth does[C] aren't moving around the sun as independently as the earth does[D] are moving around the sun at the same speed as the earth does
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It is a common sense that the earth is ( ).
A、one of the suns’ planetsB、one of the sun's planetsC、one of the sun’s planetD、one of the suns’ planet’s
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A mean sun is used as the reference for solar time for three reasons. Which reason is NOT a cause for use of a mean sun?A.The motion of the apparent sun is along the eclipticB.Measurement of time is along the celestial equatorC.The speed of the Earth's revolution is not constantD.There are variations in the Earth's rotational speed
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So Many"Earths"The Milky Way（银河）contains billions of Earth-sized planets that could support life.That's the finding of a new study.It draws on data that came from NASA's top planet-hunting telescope.A mechanical failure recently put that Kepler space telescope out of service.Kepler had played a big role in creating a census of planets orbiting some 170,000 stars.Its data have been helping astronomers predict how common planets are in our galaxy.The telescope focused on hunting planets that might have conditions similar to those on Earth.The authors of a study,published in The Proceedings of the National Academy of Sciences,conclude that between 14 and 30 out of every 100 stars,with a mass and temperature similar to the Sun,may host a planet that could support life as we know it.Such a planet would have a diameter at least as large as Earth's,but no more than twice that big.The planet also would have to orbit in a star's habitable zone.That's where the surface temperature would allow any water to exist as a liquid.The new estimate of how many planets might fit these conditions comes from studying more than 42,000 stars and identifying suitable worlds orbiting them.The scientists used those numbers to extrapolate（推算） to the rest of the stars that the telescope could not see.The estimate is rough,the authors admit.If applied to the solar system,it would define as habitable a zone starting as close to the Sun as Venus and running to as far away as Mars.Neither planet is Earthlike (although either might have been in the distant past).Using tighter limits,the researchers estimate that between 4 and 8 out of every 100 sunlike stars could host an Earth-sized world.These are ones that would take 200 to 400 days to complete a yearly orbit.Four out of every 100 sunlike stars doesn't sound like a big number.It would mean,however,that the Milky Way could host more than a billion Earth-sized planets with a chance for life.The planet that could support life might be a little bit smaller than the Earth.A:Right B:Wrong C:Not mentioned
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So Many"Earths"The Milky Way（银河）contains billions of Earth-sized planets that could support life.That's the finding of a new study.It draws on data that came from NASA's top planet-hunting telescope.A mechanical failure recently put that Kepler space telescope out of service.Kepler had played a big role in creating a census of planets orbiting some 170,000 stars.Its data have been helping astronomers predict how common planets are in our galaxy.The telescope focused on hunting planets that might have conditions similar to those on Earth.The authors of a study,published in The Proceedings of the National Academy of Sciences,conclude that between 14 and 30 out of every 100 stars,with a mass and temperature similar to the Sun,may host a planet that could support life as we know it.Such a planet would have a diameter at least as large as Earth's,but no more than twice that big.The planet also would have to orbit in a star's habitable zone.That's where the surface temperature would allow any water to exist as a liquid.The new estimate of how many planets might fit these conditions comes from studying more than 42,000 stars and identifying suitable worlds orbiting them.The scientists used those numbers to extrapolate（推算） to the rest of the stars that the telescope could not see.The estimate is rough,the authors admit.If applied to the solar system,it would define as habitable a zone starting as close to the Sun as Venus and running to as far away as Mars.Neither planet is Earthlike (although either might have been in the distant past).Using tighter limits,the researchers estimate that between 4 and 8 out of every 100 sunlike stars could host an Earth-sized world.These are ones that would take 200 to 400 days to complete a yearly orbit.Four out of every 100 sunlike stars doesn't sound like a big number.It would mean,however,that the Milky Way could host more than a billion Earth-sized planets with a chance for life.The Kepler space telescope has been in service for 15 years.A:Right B:Wrong C:Not mentioned
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So Many"Earths"The Milky Way（银河）contains billions of Earth-sized planets that could support life.That's the finding of a new study.It draws on data that came from NASA's top planet-hunting telescope.A mechanical failure recently put that Kepler space telescope out of service.Kepler had played a big role in creating a census of planets orbiting some 170,000 stars.Its data have been helping astronomers predict how common planets are in our galaxy.The telescope focused on hunting planets that might have conditions similar to those on Earth.The authors of a study,published in The Proceedings of the National Academy of Sciences,conclude that between 14 and 30 out of every 100 stars,with a mass and temperature similar to the Sun,may host a planet that could support life as we know it.Such a planet would have a diameter at least as large as Earth's,but no more than twice that big.The planet also would have to orbit in a star's habitable zone.That's where the surface temperature would allow any water to exist as a liquid.The new estimate of how many planets might fit these conditions comes from studying more than 42,000 stars and identifying suitable worlds orbiting them.The scientists used those numbers to extrapolate（推算） to the rest of the stars that the telescope could not see.The estimate is rough,the authors admit.If applied to the solar system,it would define as habitable a zone starting as close to the Sun as Venus and running to as far away as Mars.Neither planet is Earthlike (although either might have been in the distant past).Using tighter limits,the researchers estimate that between 4 and 8 out of every 100 sunlike stars could host an Earth-sized world.These are ones that would take 200 to 400 days to complete a yearly orbit.Four out of every 100 sunlike stars doesn't sound like a big number.It would mean,however,that the Milky Way could host more than a billion Earth-sized planets with a chance for life.The Earth is a planet orbiting in the Sun's habitable zone.A:Right B:Wrong C:Not mentioned
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Natural Gas1 Natural gas is produced from reservoirs deep beneath the earth's surface. It is a fossil fuel（矿物燃 料）,meaning that it is derived from organic material buried in the earth millions of years ago.The main corn- ponent of natural gas is methane（甲烷）.2 The popularity and use of clean natural gas have increased dramatically over the past 50 years as pipeline infrastructure（基础设施）has been installed to deliver it conveniently and economically to millions of residential,commercial and industrial customers worldwide.Today,natural gas service is available in all 50 states in the U.S.,and is the leading energy choice for fueling American homes and industries.More than 65 million American homes use natural gas.In fact,natural gas is the most economical source for home energyneeds,costing one-third as much as electricity. In addition to heating homes,much of the gas used in the United States is used as a raw material to manufacture a wide variety of products,from paint,to fibers for clothing,to plastics for healthcare,computing and furnishings.Natural gas is also used in a significant number of newelectricity-generating power plants.3 Natural gas is one of the safest and cleanest fuels available. It emits（发出）less pollution than other fossil fuels sources. When natural gas is burned,it produces mostly carbon dioxide（二氧化碳）and water va- por一the same substances emitted when humans breathe.Compared with some other fossil fuels,natural gas emits the least amount of carbon dioxide into the air when combusted（燃烧）一making natural gas the clea-- nest burning fossil fuel of all.4 The United States consumes about one-third of the world's natural gas output,making it the largest gas-consuming region in the world.The U.S.Department of Energy Information Administration forecasts thatnatural gas demand will grow by more than 50 percent by 2025.5 There are huge reserves of natural gas beneath the earth's surface.The largest reserves of natural gas can be found in Russia , West and North Africa and the Middle East. LNG（液化天然气）has been pro- duced domestically and imported in the United States for more than four decades.Today,the leading import-ers of LNG are Japan,Korea,France and Spain.Natural gas is stored deep______________.A:over the past 50 yearsB:beneath the earth's surfaceC:by more than 50 percentD:for more than four decadesE:as a raw materialF:for home energy needs
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So Many"Earths"The Milky Way（银河）contains billions of Earth-sized planets that could support life.That's the finding of a new study.It draws on data that came from NASA's top planet-hunting telescope.A mechanical failure recently put that Kepler space telescope out of service.Kepler had played a big role in creating a census of planets orbiting some 170,000 stars.Its data have been helping astronomers predict how common planets are in our galaxy.The telescope focused on hunting planets that might have conditions similar to those on Earth.The authors of a study,published in The Proceedings of the National Academy of Sciences,conclude that between 14 and 30 out of every 100 stars,with a mass and temperature similar to the Sun,may host a planet that could support life as we know it.Such a planet would have a diameter at least as large as Earth's,but no more than twice that big.The planet also would have to orbit in a star's habitable zone.That's where the surface temperature would allow any water to exist as a liquid.The new estimate of how many planets might fit these conditions comes from studying more than 42,000 stars and identifying suitable worlds orbiting them.The scientists used those numbers to extrapolate（推算） to the rest of the stars that the telescope could not see.The estimate is rough,the authors admit.If applied to the solar system,it would define as habitable a zone starting as close to the Sun as Venus and running to as far away as Mars.Neither planet is Earthlike (although either might have been in the distant past).Using tighter limits,the researchers estimate that between 4 and 8 out of every 100 sunlike stars could host an Earth-sized world.These are ones that would take 200 to 400 days to complete a yearly orbit.Four out of every 100 sunlike stars doesn't sound like a big number.It would mean,however,that the Milky Way could host more than a billion Earth-sized planets with a chance for life.The main task of the Kepler space telescope is to find out planets with similar conditions to Earth's.A:Right B:Wrong C:Not mentioned
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第二篇Human and the EarthIn terms of the evolution of life on Earth,human beings have just arrived.Despite their shori time on Earth,however,people have brought about enormous changes to the surface of the planet一changes far out of proportion to the interval of time they have occupied it.People have more control over their surroundings than any other species on Earth.With the combination of intelligence and manual skill(allowing us to make and use tools),people have found ways to use plant and animal resources,mineral ores,fuels,and many other materials and resources from the Earth.As the number of people on Earth increases,it becomes increasingly difficult for the population to survive on the resources of the land.The amount of land is limited.Although agricultural production can be increased by use of machinery such as tractors and the addition of fertilizer,the land ultimately can produce only so much food and no more.As the human population grows,people consume more.Clearly,some locations on Earth already have too many people;in many of these areas,future increases will surely bring about more poverty and suffering. Yet people in rich nations use proportionally far more of the available resources than people in poorer nations.As they consume these resources without restraint,they also waste large amounts of them.People are only a very small fraction of all the living things on the planet.Yet their numbers create a drain on resources that can't be renewed.For example,the amount of water on Earth is limited,this water is cleaned through natural processes.However,the natural processes for filtering water can clean only a certain amount of water by removing the pollution.Likewise,a limited amount of petroleum can be found under the Earth's surface.Petroleum is a valuable resource.Should people use it up to manufacture petrol for automobiles?As people work to control the planet and make life comfortable,are they using up resources that are needed for their survival?Why have people more control over their surroundings than any other species on Earth?A:Because of their intelligence and manual skill.B:Because they can use plant and animal resources,mineral ores and fuels.C:Because they are cleverer than any other animals on Earth.D:Both A and B.
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第一篇The Northern LightsThe sun is stormy and has its own kind of weather.It is so hot and active that even the Sun's gravity cannot hold its atmosphere in check!Energy flows away from the Sun toward the Earth in a stream of electrified particles that move at speeds around a million miles per hour.These particles are called plasma （等离子体）,and the stream of plasma coming from the Sun is called the solar wind.The more active the Sun,the stronger the solar wind.The solar wind constantly streams toward the Earth,but don't worry because a protective magnetic field surrounds our planet.The same magnetic field that makes your compass point north also steers the particles from the Sun to the north and south poles.The charged particles become trapped in magnetic belts around the Earth.When a large blast of solar wind crashes into the Earth's magnetic field,the magnetic field first gets squeezed and then the magnetic field lines break and reconnect.The breaking and reconnecting of the magnetic field lines can cause atomic particles called electrons trapped in the belts to fall into tile Earth's atmosphere at the poles.As the electrons fall to the Earth,they collide with gas molecules in the atmosphere,creating flashes of light in the sky.Each atmospheric gas glows a different color.Oxygen and nitrogen glows red and green arid nitrogen glows violet purple.As these various colors glow and dance in the night sky,they create the Northern Lights and the Southern Lights.Watching auroras（北极光）is fun and exciting, but normally you can only see them in places far north like Alaska and Canada.The movement of the aurora across the sky is usually slow enough to easily follow with your eyes but they can also pulsate（跳动）,flicker（闪烁）,or even move like waves.During solar maximum,5 auroras are seen as far south as Florida,even Mexico!Auroras often seem to be very close to the ground,but the lowest aurora is still about 100 kilometers above the ground,a distance much higher than clouds are formed or airplanes can fly.A typical aurora band can be thousands of kilometers long,a few hundred kilometers high,but only a few hundred meters thick.We hope you are able to travel to far north places like the Arctic Circle and see the Northern Lights at least once during your lifetime.We know you will never forget it!What happens when solar wind comes to the Earth?A:It is trapped in magnetic belts around the Earth.B:A protective magnetic field is formed at the same time.C:It destroys the protective magnetic field surrounding the Earth.D:It breaks magnetic field lines and does severe damage to the Earth.
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Uranus, ________ is much more massive than the Earth, seems to have been tipped over so that it lies on its side.A.what
B.who
C.that
D.winch
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Nowhere are the realities of______climate change more apparent than at Earth's thawing poles.A.human-driving
B.human-drive
C.human-driven
D.human-drived
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Modern Sun Worshippers People travel for a lot of reasons.Some tourists go to see battlefields or religious shrines.Others are looking for culture,or simply want to have their pictures taken in front of famous places.But most European tourists are looking for a sunny beach to lie on. Northern Europeans are willing to pay a lot of money and put up with a lot of inconveniences for the sun because they have so little of it.Residents of cities like London,Copenhagen,and Amsterdam spend a lot of their winter in the dark because the days are so short,and much of the rest of the year in the rain.This is the reason why the Mediterranean has always attracted them.Every summer,more than 25 million people travel to Mediterranean resorts and beaches for their vacation.They all come for the same reason:sun! The huge crowds mean lots of money for the economies of Mediterranean countries.Italy's30,000 hotels are booked solid every summer.And 13 million people camp out on French beaches,parks,and roadsides.Spain's long sandy coastline attracts more people than anywhere else.37 million tourists visit yearly,or one tourist for every person living in Spain. But there are signs that the area is getting more tourism than it can handle.The Mediterranean is already one of the most polluted seas on earth.And with increased tourism,it's getting worse.The French can't figure out what to do with all the garbage left by campers around St.Tropez.And in many places, swimming is dangerous because of pollution. None of this,however,is-spoiling anyone's fun.The Mediterranean gets more popular every year with tourists.Obviously,they don't go there for clean water and solitude.They tolerate traffic jams and seem to like crowded beaches.They don't even mind the pollution.No matter how dirty the water is,the coastline still looks beautiful.And as long as the sun shines,it's still better than sitting in the cold rain in Berlin,Iondon,or Oslo.According to the passage,France attracts more tourists than the others.A:Right B:Wrong C:Not mentioned
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New Comet FoundThere's a newfound comet closing in on the sun,and when it gets here in 2013,you may be able to see it with your naked eye.Astronomers stumbled upon the icy interloper on June 5 while searching for potentially hazardous asteroids（小行星）.Equipped with the world's largest digital camera , the University of Hawaii's Pan-STARRS team snagged a faint image of the odd object while it was more than 700 million miles away , between the orbits of Jupiter（木星）and Saturn（土星）."Almost everything we find is an asteroid,but this object was suspicious,"said Richard Wainscoat,co-discoverer of the comet and an astronomer at the University of Hawaii."Unlike asteroids, which appear point-like in images,the telltale sign that gave it away was its fuzzy appearance."By March 2013 the comet,named C/2011 L4(PANSTARRS),is expected to come within 30 million miles of the sun一closer even than the innermost（最深处）planet, Mercury（水星）.When the comet makes its closest approach to the sun,most of its ices will vaporize,adding to its hazy envelope of gas and dust and producing the familiar tail. This denser envelope,or coma, should boost the comet to peak brightness,making it potentially visible to the naked eye low in the western horizon just after sunset.While there is no danger of collision with Earth,preliminary calculations of the comet's orbit show that this may be its first and final trip through the solar system."It may be coming around the sun for the first and only time,only to be ejected from the solar system,never to return,"Wainscoat said."Since we don't have a lot of data on it,we really don't know the orbit well enough right now, and it will take up to two months of observations to find out."Astronomers believe C/2011 L4 may be a runaway from the Oort cloud（奥尔特云）,a reservoir of billions of hibernating（蛰伏）comets that orbits about 100,000 times farther than the distance between Earth and the sun.The fact that it's going around the back of the sun from our point of view may ultimately affect the comet's visibility,but a lot will depend on how close the body actually gets to the sun.Also, whether the comet is north or south of the sun when it reaches peak brightness will determine which hemisphere on Earth gets the better view.The newfound comet is made from mercury.A:Right B:Wrong C:Not mentiond
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Weight on and off the Earth We are so used to.our life on the surface of the earth that it can be quite an effort for our mind to break free of all the ideas that we take for granted.Because we can feel that things are heavy,we think of "weight"as being a fixed quality in an object,but it is not really fixed at all.If you could take a one-pound packet of butter 4,000 miles out from the earth,it would weigh only a quarter of a pound. Why would things weigh only a quarter as much as they do at the surface of the earth if we took them 4,000 miles out into space?The reason is this:all objects have a natural attraction for all other objects;this is called gravitational attraction.But this power of attraction between two obects gets weaker as they get farther apart.When the butter was at the surface of the earth,it was 4,000 miles from the center.When we took the butter 4,000 miles out,it was 8,000 miles from the center,which is twice the distance.If you double the distance between two objects,their gravitational attraction decreases two times two.If you treble the distance, it gets nine times weaker(three times three)and so on. So this is one of the first things we need to remember that the weight of an object in space is not the same as its weight on the surface of the earth. What about the weight of our pound of butter on the surface of the moon?At the distance the puii of the earth is about 4,000 times smaller than it is here on the surface,so we can forget all about the earth-pull on our butter. On the other hand,on the moon there will be an attraction between the butter and the moon,but the butter will weigh only about one-sixth as much as it does on the earth.This is because the moon is so much smaller than the earth.The amount of gravitational pull that a body produces depends on the amount of material in it.A packet of butter has a gravitational pull of its own;but this is very small in relation to the pull of something as large as the moon,or the earth,or the sun.According to the passage,"weight"should be understood in the sense thatA:it is fixed if it is outside the earth's gravitational puliB:it decreases four times when it is 4,000 miles from the earth's centerC:it varies with the change of the gravitational attraction between two objectsD:things increase in amount as they are closer to the earth's surface
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New Comet FoundThere's a newfound comet closing in on the sun,and when it gets here in 2013,you may be able to see it with your naked eye.Astronomers stumbled upon the icy interloper on June 5 while searching for potentially hazardous asteroids（小行星）.Equipped with the world's largest digital camera , the University of Hawaii's Pan-STARRS team snagged a faint image of the odd object while it was more than 700 million miles away , between the orbits of Jupiter（木星）and Saturn（土星）."Almost everything we find is an asteroid,but this object was suspicious,"said Richard Wainscoat,co-discoverer of the comet and an astronomer at the University of Hawaii."Unlike asteroids, which appear point-like in images,the telltale sign that gave it away was its fuzzy appearance."By March 2013 the comet,named C/2011 L4(PANSTARRS),is expected to come within 30 million miles of the sun一closer even than the innermost（最深处）planet, Mercury（水星）.When the comet makes its closest approach to the sun,most of its ices will vaporize,adding to its hazy envelope of gas and dust and producing the familiar tail. This denser envelope,or coma, should boost the comet to peak brightness,making it potentially visible to the naked eye low in the western horizon just after sunset.While there is no danger of collision with Earth,preliminary calculations of the comet's orbit show that this may be its first and final trip through the solar system."It may be coming around the sun for the first and only time,only to be ejected from the solar system,never to return,"Wainscoat said."Since we don't have a lot of data on it,we really don't know the orbit well enough right now, and it will take up to two months of observations to find out."Astronomers believe C/2011 L4 may be a runaway from the Oort cloud（奥尔特云）,a reservoir of billions of hibernating（蛰伏）comets that orbits about 100,000 times farther than the distance between Earth and the sun.The fact that it's going around the back of the sun from our point of view may ultimately affect the comet's visibility,but a lot will depend on how close the body actually gets to the sun.Also, whether the comet is north or south of the sun when it reaches peak brightness will determine which hemisphere on Earth gets the better view.Astronomers found a new comet by naked eye.A:Right B:Wrong C:Not mentiond
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Where Did the Earth's Water Come From?Earth is located within the"snow line"of the solar system,the region closest to the Sun where H2 0 is primarily in liquid or gaseous form,if at all.______(46)The snow line phenomena is reflected in the water content of planets like Mercury,Venus,and Mars. Water is absent on Mercury.On Venus,H2O only exists as a trace element in the atmosphere.Mars only has a thin veneer of ice in its polar regions.In general,water is rare within the snow line.Why does Earth have so much water relative to the other inner planets?71%of the surface is covered in the oceans,more than half of which is deeper than 3,000 meters,with an approximate total volume of 1.3 billion cu km.______(47)There are various theories as to where all the Earth's water came from,but several theories have fared better than the others.______(48)When the Earth was in the process of forming,with a radius just 40%smaller than at present,it would have had enough gravity to hold on to a tenuous atmosphere with water vapor. The first water vapor on the planet would have come from the planet's internals,where volatile(low weight)chemicals would have a tendency to float to the top,and heavy chemicals(iron and nickel)would sink.Though the first of Earth's water came about through volcanism,this alone probably didn't produce enough to form stable pools on the surface.______(49)Comparing the isotope ratios of water on Earth and water from comets and asteroids has revealed that the majority of the Earth's water comes from asteroids.Throughout its history,Earth's water has increased in volume due to biological processes. In the early seas of Earth,hydrogen sulfide would have been in great supply,which,when reacted with carbon dioxide from the atmosphere during photosynthesis in sulfide-reducing bacteria,would have produced hydrogen,sulfur,and water.______(50)________（49）A: More water was added to the planet during several hypothesized large impacts from asteroids from the outer asteroid belt.B:We know that the oceans existed as early as 100 million years after the formation of the Earth.C:Still,the oceans only make up 0.023%of the Earth's total mass.D:Astronomers say Earth s water may have come from space.E:The snow line is located in the outerasteroid belt,between the orbits of Mars and Jupiter. F: Many geologists believe that the majority of Earth's water generated through this process.
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New Comet FoundThere's a newfound comet closing in on the sun,and when it gets here in 2013,you may be able to see it with your naked eye.Astronomers stumbled upon the icy interloper on June 5 while searching for potentially hazardous asteroids（小行星）.Equipped with the world's largest digital camera , the University of Hawaii's Pan-STARRS team snagged a faint image of the odd object while it was more than 700 million miles away , between the orbits of Jupiter（木星）and Saturn（土星）."Almost everything we find is an asteroid,but this object was suspicious,"said Richard Wainscoat,co-discoverer of the comet and an astronomer at the University of Hawaii."Unlike asteroids, which appear point-like in images,the telltale sign that gave it away was its fuzzy appearance."By March 2013 the comet,named C/2011 L4(PANSTARRS),is expected to come within 30 million miles of the sun一closer even than the innermost（最深处）planet, Mercury（水星）.When the comet makes its closest approach to the sun,most of its ices will vaporize,adding to its hazy envelope of gas and dust and producing the familiar tail. This denser envelope,or coma, should boost the comet to peak brightness,making it potentially visible to the naked eye low in the western horizon just after sunset.While there is no danger of collision with Earth,preliminary calculations of the comet's orbit show that this may be its first and final trip through the solar system."It may be coming around the sun for the first and only time,only to be ejected from the solar system,never to return,"Wainscoat said."Since we don't have a lot of data on it,we really don't know the orbit well enough right now, and it will take up to two months of observations to find out."Astronomers believe C/2011 L4 may be a runaway from the Oort cloud（奥尔特云）,a reservoir of billions of hibernating（蛰伏）comets that orbits about 100,000 times farther than the distance between Earth and the sun.The fact that it's going around the back of the sun from our point of view may ultimately affect the comet's visibility,but a lot will depend on how close the body actually gets to the sun.Also, whether the comet is north or south of the sun when it reaches peak brightness will determine which hemisphere on Earth gets the better view.The ices of the comet will vaporize while heading to the sun.A:Right B:Wrong C:Not mentiond
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共用题干
New Comet FoundThere's a newfound comet closing in on the sun,and when it gets here in 2013,you may be able to see it with your naked eye.Astronomers stumbled upon the icy interloper on June 5 while searching for potentially hazardous asteroids（小行星）.Equipped with the world's largest digital camera , the University of Hawaii's Pan-STARRS team snagged a faint image of the odd object while it was more than 700 million miles away , between the orbits of Jupiter（木星）and Saturn（土星）."Almost everything we find is an asteroid,but this object was suspicious,"said Richard Wainscoat,co-discoverer of the comet and an astronomer at the University of Hawaii."Unlike asteroids, which appear point-like in images,the telltale sign that gave it away was its fuzzy appearance."By March 2013 the comet,named C/2011 L4(PANSTARRS),is expected to come within 30 million miles of the sun一closer even than the innermost（最深处）planet, Mercury（水星）.When the comet makes its closest approach to the sun,most of its ices will vaporize,adding to its hazy envelope of gas and dust and producing the familiar tail. This denser envelope,or coma, should boost the comet to peak brightness,making it potentially visible to the naked eye low in the western horizon just after sunset.While there is no danger of collision with Earth,preliminary calculations of the comet's orbit show that this may be its first and final trip through the solar system."It may be coming around the sun for the first and only time,only to be ejected from the solar system,never to return,"Wainscoat said."Since we don't have a lot of data on it,we really don't know the orbit well enough right now, and it will take up to two months of observations to find out."Astronomers believe C/2011 L4 may be a runaway from the Oort cloud（奥尔特云）,a reservoir of billions of hibernating（蛰伏）comets that orbits about 100,000 times farther than the distance between Earth and the sun.The fact that it's going around the back of the sun from our point of view may ultimately affect the comet's visibility,but a lot will depend on how close the body actually gets to the sun.Also, whether the comet is north or south of the sun when it reaches peak brightness will determine which hemisphere on Earth gets the better view.C/2011 L4 will hit Earth in 2013.A:Right B:Wrong C:Not mentiond
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根据以下材料，回答题
In a telephone survey of more than 2,000adults,21% said they believed the sun revolved (旋转) around the earth. An 51 7% did not know which revolvedaround 52. I have no doubt that 53 all of these people were 54 inschool that the earth revolves around the sun: 55 may even have written it 56 a test. But they never 57 their incorrect mental models ofplanetary(行星的) 58 because their everydayobservations didn′t support 59 their teachers told them: People seethe sun "moving" 60 the sky as morning turns to night, and theearth seems stationary(静止的) 61 that ishappening.
Students can learn the right answers 62 heart in class, and yet never combinedthem 63 their working models of the world.The objectively correct answer the professor accepts and the 64 personal understanding of the world can 65 side by side, each unaffected bythe other.
Outside of class, the students like to seethe 66 model because it has always worked well 67 that circumstance. Unless professorsaddress 68 errors in students′ personal models of the world, studentsare not 69 to replace them with 70 one.
A.adult′s
B.teacher's
C.scientist's
D.student's
考题
单选题A mean sun is used as the reference for solar time for three reasons. Which reason is NOT a cause for use of a mean sun?（）A
The motion of the apparent sun is along the eclipticB
Measurement of time is along the celestial equatorC
The speed of the Earth's revolution is not constantD
There are variations in the Earth's rotational speed
考题
单选题Without the sun’s light _____ the earth’s surface, it would be so cold that life could not exist on the earth.A
warmsB
warmedC
warmingD
to warm
考题
单选题During the Clinton presidency, the U.S. enjoyed more than any time in its history peace and economic well being.A
the U.S. enjoyed more than any time in its history peace and economic well beingB
the U.S. enjoying more than any other time in its history peace and economic well beingC
more peace and economic well being was enjoyed by the U.S. than any other timeD
economic peace and well being was enjoyed by the U.S. more so than any other ~ time in the country’s historyE
the U.S. enjoyed more peace and economic well being than at any other time in its history
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