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Many people believe the glare from snow causes snow blindness.Yet, with dark glasses or not, they find themselves suffering from headaches and watering eyes, and even snowblindness, when exposed to several hours of "snow light". The United States Army has now determined that the glare from snow does not cause snow-blindness in troops in a snow-covered country.Rather, a mans eyes frequently find nothing to focus on in a broad expanse of a snow-covered area.So his gaze continually shifts and jumps back and forth over the entire landscape in search of something to look at.Finding nothing, hour after hour, the eyes never stop searching and the eyeballs become sore and the eye muscle aches.Nature balances this annoyance by producing more and more liquid which covers the eyeballs.The liquid covers the eyeballs in increasing quantity until vision blurs.And the result is total,even though temporary,snowblindness. Experiments led the Army to a simple method of overcoming this problem.Scouts ahead of a main body of troops are trained to shake snow from evergreen bushes, creating a dotted line as they cross completely snow-covered landscape.Even the scouts themselves throw lightweight, dark-colored objects ahead on which they too can focus. The men following can then see something.Their gaze is arrested.Their eyes focus on a bush and having found something to see, stop searching through the snow- blanketed landscape.By focusing their attention on one object at a time, the man can cross the snow withoutbecoming hopelessly snowblind or lost.In this way the problem of crossing a solid white area is overcome.
The eyeballs become sore and the eye muscles ache because______.
A．tears cover the eyeballs
B．the eyes are annoyed by blinding sunlight
C．the eyes are annoyed by blinding snow
D．there is nothing to focus on
参考答案
更多 “ Many people believe the glare from snow causes snow blindness.Yet, with dark glasses or not, they find themselves suffering from headaches and watering eyes, and even snowblindness, when exposed to several hours of "snow light". The United States Army has now determined that the glare from snow does not cause snow-blindness in troops in a snow-covered country.Rather, a mans eyes frequently find nothing to focus on in a broad expanse of a snow-covered area.So his gaze continually shifts and jumps back and forth over the entire landscape in search of something to look at.Finding nothing, hour after hour, the eyes never stop searching and the eyeballs become sore and the eye muscle aches.Nature balances this annoyance by producing more and more liquid which covers the eyeballs.The liquid covers the eyeballs in increasing quantity until vision blurs.And the result is total,even though temporary,snowblindness. Experiments led the Army to a simple method of overcoming this problem.Scouts ahead of a main body of troops are trained to shake snow from evergreen bushes, creating a dotted line as they cross completely snow-covered landscape.Even the scouts themselves throw lightweight, dark-colored objects ahead on which they too can focus. The men following can then see something.Their gaze is arrested.Their eyes focus on a bush and having found something to see, stop searching through the snow- blanketed landscape.By focusing their attention on one object at a time, the man can cross the snow withoutbecoming hopelessly snowblind or lost.In this way the problem of crossing a solid white area is overcome.The eyeballs become sore and the eye muscles ache because______.A．tears cover the eyeballsB．the eyes are annoyed by blinding sunlightC．the eyes are annoyed by blinding snowD．there is nothing to focus on ” 相关考题
考题
– It’s starting to snow. – Starting to snow?().
(A) They are ready for the snow(B) It is typical December weather(C) Once it starts, it’ll snow a lot(D) It has been snowing for some time
考题
If your urine makes the snow dark yellow，you are becoming ______．A.constipatedB.dehydratedC.frostbitedD.cold diuresic
考题
Many people believe the glare from snow causes snow-blindness． Yet, dark glasses or not,they find themselves suffering from headaches and watering eyes, and even snow-blindness, when exposed to several hours of "snow light"．
The United States Army has now determined that glare from snow does not cause snow-
blindness in troops in a snow-covered country． Rather, a man's eyes frequently find nothing to focus on in a broad expanse of barren snow-covered terrain． So his gaze continually shifts and jumps back and forth over the entire landscape in search of something to look at． Finding nothing,hour after hour, the eyes never stop searching and the eyeballs become sore and the eye musclesache． Nature offsets this irritation by producing more and fluid which covers the eyeball． The fluid covers the eyeball in increasing quantity until vision blurs, then is observed, and the result is
total, even though temporary, snow-blindness．
Experiments led the Army to a simple method of overcoming this problem． Scouts ahead of a main body of troops are trained to shake snow from evergreen bushes, creating a dotted line as they cross completely snow-covered landscape． Even the scouts themselves throw lightweight, dark colored objects ahead on which they too can focus． The men following can then see something．Their gaze is arrested． Their eyes focus on a bush and having found something to see, stop scouring the snow-blanketed landscape． By focusing their attention on one object at a time, the men can cross the snow without becoming hopelessly snow-blind or lost． In this way the problem of crossing a solid white terrain is overcome．
?The scouts shake snow from evergreen bushes in order to__________ ．A.give the men behind something to see
B.beautify the landscape
C.warm themselves in the cold
D.prevent the men behind from losing their way
考题
Many people believe the glare from snow causes snow-blindness． Yet, dark glasses or not,they find themselves suffering from headaches and watering eyes, and even snow-blindness, when exposed to several hours of "snow light"．
The United States Army has now determined that glare from snow does not cause snow-
blindness in troops in a snow-covered country． Rather, a man's eyes frequently find nothing to focus on in a broad expanse of barren snow-covered terrain． So his gaze continually shifts and jumps back and forth over the entire landscape in search of something to look at． Finding nothing,hour after hour, the eyes never stop searching and the eyeballs become sore and the eye musclesache． Nature offsets this irritation by producing more and fluid which covers the eyeball． The fluid covers the eyeball in increasing quantity until vision blurs, then is observed, and the result is
total, even though temporary, snow-blindness．
Experiments led the Army to a simple method of overcoming this problem． Scouts ahead of a main body of troops are trained to shake snow from evergreen bushes, creating a dotted line as they cross completely snow-covered landscape． Even the scouts themselves throw lightweight, dark colored objects ahead on which they too can focus． The men following can then see something．Their gaze is arrested． Their eyes focus on a bush and having found something to see, stop scouring the snow-blanketed landscape． By focusing their attention on one object at a time, the men can cross the snow without becoming hopelessly snow-blind or lost． In this way the problem of crossing a solid white terrain is overcome．
Snow-blindness may be avoided by__________ A.concentrating to the solid white terrain
B.searching for something to look at in snow-covered terrain
C.providing the eyes with something to focus on
D.covering the eyeballs with fluid
考题
Many people believe the glare from snow causes snow-blindness． Yet, dark glasses or not,they find themselves suffering from headaches and watering eyes, and even snow-blindness, when exposed to several hours of "snow light"．
The United States Army has now determined that glare from snow does not cause snow-
blindness in troops in a snow-covered country． Rather, a man's eyes frequently find nothing to focus on in a broad expanse of barren snow-covered terrain． So his gaze continually shifts and jumps back and forth over the entire landscape in search of something to look at． Finding nothing,hour after hour, the eyes never stop searching and the eyeballs become sore and the eye musclesache． Nature offsets this irritation by producing more and fluid which covers the eyeball． The fluid covers the eyeball in increasing quantity until vision blurs, then is observed, and the result is
total, even though temporary, snow-blindness．
Experiments led the Army to a simple method of overcoming this problem． Scouts ahead of a main body of troops are trained to shake snow from evergreen bushes, creating a dotted line as they cross completely snow-covered landscape． Even the scouts themselves throw lightweight, dark colored objects ahead on which they too can focus． The men following can then see something．Their gaze is arrested． Their eyes focus on a bush and having found something to see, stop scouring the snow-blanketed landscape． By focusing their attention on one object at a time, the men can cross the snow without becoming hopelessly snow-blind or lost． In this way the problem of crossing a solid white terrain is overcome．
To prevent headaches, watering eyes and blindness caused by the glare from snow, dark glasses are__________ ．A.indispensible
B.useful
C.ineffective
D.available
考题
Many people believe the glare from snow causes snow-blindness． Yet, dark glasses or not,they find themselves suffering from headaches and watering eyes, and even snow-blindness, when exposed to several hours of "snow light"．
The United States Army has now determined that glare from snow does not cause snow-
blindness in troops in a snow-covered country． Rather, a man's eyes frequently find nothing to focus on in a broad expanse of barren snow-covered terrain． So his gaze continually shifts and jumps back and forth over the entire landscape in search of something to look at． Finding nothing,hour after hour, the eyes never stop searching and the eyeballs become sore and the eye musclesache． Nature offsets this irritation by producing more and fluid which covers the eyeball． The fluid covers the eyeball in increasing quantity until vision blurs, then is observed, and the result is
total, even though temporary, snow-blindness．
Experiments led the Army to a simple method of overcoming this problem． Scouts ahead of a main body of troops are trained to shake snow from evergreen bushes, creating a dotted line as they cross completely snow-covered landscape． Even the scouts themselves throw lightweight, dark colored objects ahead on which they too can focus． The men following can then see something．Their gaze is arrested． Their eyes focus on a bush and having found something to see, stop scouring the snow-blanketed landscape． By focusing their attention on one object at a time, the men can cross the snow without becoming hopelessly snow-blind or lost． In this way the problem of crossing a solid white terrain is overcome．
?When the eyes are sore tears are produced toA.clear the vision
B.remedy snow-blindness
C.ease the irritation
D.loosen the muscles
考题
Many people believe the glare from snow causes snow-blindness． Yet, dark glasses or not,they find themselves suffering from headaches and watering eyes, and even snow-blindness, when exposed to several hours of "snow light"．
The United States Army has now determined that glare from snow does not cause snow-
blindness in troops in a snow-covered country． Rather, a man's eyes frequently find nothing to focus on in a broad expanse of barren snow-covered terrain． So his gaze continually shifts and jumps back and forth over the entire landscape in search of something to look at． Finding nothing,hour after hour, the eyes never stop searching and the eyeballs become sore and the eye musclesache． Nature offsets this irritation by producing more and fluid which covers the eyeball． The fluid covers the eyeball in increasing quantity until vision blurs, then is observed, and the result is
total, even though temporary, snow-blindness．
Experiments led the Army to a simple method of overcoming this problem． Scouts ahead of a main body of troops are trained to shake snow from evergreen bushes, creating a dotted line as they cross completely snow-covered landscape． Even the scouts themselves throw lightweight, dark colored objects ahead on which they too can focus． The men following can then see something．Their gaze is arrested． Their eyes focus on a bush and having found something to see, stop scouring the snow-blanketed landscape． By focusing their attention on one object at a time, the men can cross the snow without becoming hopelessly snow-blind or lost． In this way the problem of crossing a solid white terrain is overcome．
A suitable title for this passage would be __________ ．A.Snow-Blindness and How to Overcome It
B.Nature's Cure for Snow Blindness
C.Soldiers in the Snow
D.Snow Vision
考题
Many people believe the glare from snow causes snow-blindness. Yet, dark glasses or not, they find themselves suffering from headaches and watering eyes, and even snow-blindness, when exposed to several hours of "snow light".
The United States Army has now determined that glare from snow does not cause snow- blindness in troops in a snow-covered country. Rather, a man's eyes frequently find nothing to focus on in a broad expanse of barren snow-covered terrain. So his gaze continually shifts and jumps back and forth over the entire landscape in search of something to look at. Finding nothing, hour after hour, the eyes never stop searching and the eyeballs become sore and the eye muscles ache. Nature offsets this irritation by producing more and fluid which covers the eyeball. The fluid
covers the eyeball in increasing quantity until vision blurs,then is observed, and the result is total, even though temporary, snow-blindness.
Experiments led the Army to a simple method of overcoming this problem. Scouts ahead of a main body of troops are trained to shake snow from evergreen bushes, creating a dotted line as they cross completely snow-covered landscape. Even the scouts themselves throw lightweight, dark colored objects ahead on which they too can focus. The men following can then see something. Their gaze is arrested. Their eyes focus on a bush and having found something to see, stop scouring the snow-blanketed landscape. By focusing their attention on one object at a time, the men can cross the snow without becoming hopelessly snow-blind or lost. In this way the problem of crossing a solid white terrain is overcome.
To prevent headaches, watering eyes and blindness caused by the glare from snow, dark glasses are__________.A. indispensible
B. useful
C. ineffective
D. available
考题
There are many stereotypes about the character of people in various parts of the United States．In the Northeast and Midwest,people are said to be closed and private．In the South and West,however,they are often thought of as being more open and hospitable．Ask someone from St．Louis where the nearest sandwich shop is,and he or she will politely give you directions．A New Yorker might eye you at first and after deciding it is safe to talk to you,might give you a rather unexpected explanation．A person from Georgia might be very kind about directing you and even suggest some different places to eat．A Texan just might take you to the place and treat you to lunch.
American stereotypes are abundant．New Englanders are often thought of as being friendly and helpful．Southerners are known for their hospitality and warmth．People from the western part of the United States are often considered very outgoing．These differences in character can be traced to different factors such as climate,living conditions,and historical development.
When travelling from place to place,Americans themselves are often surprised at the differing degrees of friendliness in the United States.
The main idea of the passage is__.A.even Americans are surprised at the big differences among themselves
B.there are many differences in character in different parts of the USA
C.there are many reason for the differences
D.stereotypes about people are not necessarily true
考题
There are many stereotypes about the character of people in various parts of the United States．In the Northeast and Midwest,people are said to be closed and private．In the South and West,however,they are often thought of as being more open and hospitable．Ask someone from St．Louis where the nearest sandwich shop is,and he or she will politely give you directions．A New Yorker might eye you at first and after deciding it is safe to talk to you,might give you a rather unexpected explanation．A person from Georgia might be very kind about directing you and even suggest some different places to eat．A Texan just might take you to the place and treat you to lunch.
American stereotypes are abundant．New Englanders are often thought of as being friendly and helpful．Southerners are known for their hospitality and warmth．People from the western part of the United States are often considered very outgoing．These differences in character can be traced to different factors such as climate,living conditions,and historical development.
When travelling from place to place,Americans themselves are often surprised at the differing degrees of friendliness in the United States.
Which of the following is true according to the passage?A.New Yorkers are usually open with stranger
B.People from the South are usually considered good host
C.The friendliest Americans travel from place to plac
D.Different parts have different customs and habit
考题
资料：When we see well，we do not think about our eyes very often. It is only when we cannot see perfectly that we realize how important our eyes are.
People who are near-sighted can only see things that are very close to their eyes，Everything else seems blurry（=unclear）.Many people who do a lot of work，such as writing，reading and sewing become near-sighted.
People who are far-sighted suffer from just the opposite problem. They can see things that are far away，but they have difficulty in reading a book unless they hold it at arm’s length. If they want to do much reading，they must get glasses，too.
Other people do not see clearly because their eyes are not exactly the right shape. They have what is called astigmatism. This，too，can be corrected by glasses. Some people’s eyes become cloudy because of cataracts. Long ago these people often became blind. Now，however，it is possible to operate on the cataracts and remove them.
Having two good eyes is important for judging distances. Each eye sees things from a slightly different angle. To prove this to yourself，look at an object out of one eye；Then look at the same object out of your other eye. You will find the object’s relation to the background and other things around it has changed. The difference between these two different eye views helps us to judge how far away an object is. People who have only one eye cannot judge distance as people with two eyes.
When things far away seem indistinct， one is probably______.A.astigmatic
B.far-sighted
C.suffering from cataracts
D.near-sighted
考题
资料：When we see well，we do not think about our eyes very often. It is only when we cannot see perfectly that we realize how important our eyes are.
People who are near-sighted can only see things that are very close to their eyes，Everything else seems blurry（=unclear）.Many people who do a lot of work，such as writing，reading and sewing become near-sighted.
People who are far-sighted suffer from just the opposite problem. They can see things that are far away，but they have difficulty in reading a book unless they hold it at arm’s length. If they want to do much reading，they must get glasses，too.
Other people do not see clearly because their eyes are not exactly the right shape. They have what is called astigmatism. This，too，can be corrected by glasses. Some people’s eyes become cloudy because of cataracts. Long ago these people often became blind. Now，however，it is possible to operate on the cataracts and remove them.
Having two good eyes is important for judging distances. Each eye sees things from a slightly different angle. To prove this to yourself，look at an object out of one eye；Then look at the same object out of your other eye. You will find the object’s relation to the background and other things around it has changed. The difference between these two different eye views helps us to judge how far away an object is. People who have only one eye cannot judge distance as people with two eyes.
We should take good care of our eyes______.
A.even if we can see well
B.only when we cannot see perfectly
C.only when we realize how important our eyes are
D.only when we can see well
考题
共用题干
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.
考题
共用题干
The Dangers of Secondhand SmokeMost people know that cigarette smoking is harmful to their health.Scientific research shows that it causes many kinds of diseases.In fact,many people who smoke get lung cancer. However,Edward Gilson has lung cancer,and he has never smoked cigarettes.He lives with his wife Evelyn,who has smoked about a pack of cigarettes a day throughout their marriage.________(46)No one knows for sure why Mr. Gilson has lung cancer. Nevertheless,doctors believe that secondhand smoke may cause lung cancer in people who do not smoke because nonsmokers often breathe in the smoke from other people's cigarettes.________(47)The US Environmental Protection Agency reports that about 53,000 people die in the United States each year as a result of exposure to secondhand smoke.The smoke that comes from a lit cigarette contains many different poisonous chemicals.In the past, scientists did not think that these chemicals could harm a nonsmoker's health._________(48)They discovered that even nonsmokers had unhealthy amounts of these toxic chemicals in their bodies.As a matter of fact,almost all of us breathe tobacco smoke at times,whether we realize it or not. For example,we can not avoid secondhand smoke in restaurants,hotels and other public places.Even though many public places have nonsmoking areas,smoke flows in from the areas where smoking is permitted.It is even harder for children to avoid secondhand smoke._________(49)Research shows that chil- dren who are exposed to secondhand smoke are sick more often than children who live in homes where no one smokes and that the children of smokers are more than twice as likely to develop lung cancer when they are adults as are children of nonsmokers.The risk is even higher for children who live in homes where both parents smoke.People are becoming very aware of the dangers of secondhand smoke._________（50)__________（50）A:Recently,though,scientists changed their opinion after they studied a large group of nonsmokers.B:The Gilsons have been married for 35 years.C:This smoke is called secondhand smoke.D:However,secondhand smoke is dangerous to all people,old or young.E:As a result,they have passed laws which prohibit people from smoking in many public places.F: In the United States,nine million children under the age of five live in homes with at least one smoker.
考题
Questions 21 to 25 are based on the following passage.
Lead deposits, which accumulated in soil and snow during the 1960’s and 70’s, were primarily the result of leaded gasoline emissions originating in the United States. In the twenty years that the Clean Air Act has mandated unleaded gas use in the United States, the lead accumulation worldwide has decreased significantly.
A study published recently in the journal Nature shows that air-borne leaded gas emissions from the United States were the leading contributor to the high concentration of lead in the snow in Greenland. The new study is a result of the continued research led by Dr. Charles Boutron, an expert on the impact of heavy metals on the environment at the National Center for Scientific Research in France. A study by Dr. Boutron published in 1991 showed that lead levels in arctic (北极的) snow were declining.
In his new study, Dr. Boutron found the ratios of the different forms of lead in the leaded gasoline used in the United States were different from the ratios of European, Asian and Canadian gasolines and thus enabled scientists to differentiate (区分) the lead sources. The dominant lead ratio found in Greenland snow matched that found in gasoline from the United States.
In a study published in the journal Ambio, scientists found that lead levels in soil in the Northeastern United States had decreased markedly since the introduction of unleaded gasoline.
Many scientists had believed that the lead would stay in soil and snow for a longer period.
The authors of the Ambio study examined samples of the upper layers of soil taken from the same sites of 30 forest floors in New England, New York and Pennsylvania in 1980 and in 1990. The forest environment processed and redistributed the lead faster than the scientists had expected.
Scientists say both studies demonstrate that certain parts of the ecosystem (生态系统) respond rapidly to reductions in atmospheric pollution, but that these findings should not be used as a license to pollute.
The authors of the Ambio study have found that（）A、forests get rid of lead pollution faster than expectedB、lead accumulations in forests are more difficult to deal withC、lead deposits are widely distributed in the forests of the USD、the upper layers of soil in forests are easily polluted by lead emissions
考题
Questions 21 to 25 are based on the following passage.
Lead deposits, which accumulated in soil and snow during the 1960’s and 70’s, were primarily the result of leaded gasoline emissions originating in the United States. In the twenty years that the Clean Air Act has mandated unleaded gas use in the United States, the lead accumulation worldwide has decreased significantly.
A study published recently in the journal Nature shows that air-borne leaded gas emissions from the United States were the leading contributor to the high concentration of lead in the snow in Greenland. The new study is a result of the continued research led by Dr. Charles Boutron, an expert on the impact of heavy metals on the environment at the National Center for Scientific Research in France. A study by Dr. Boutron published in 1991 showed that lead levels in arctic (北极的) snow were declining.
In his new study, Dr. Boutron found the ratios of the different forms of lead in the leaded gasoline used in the United States were different from the ratios of European, Asian and Canadian gasolines and thus enabled scientists to differentiate (区分) the lead sources. The dominant lead ratio found in Greenland snow matched that found in gasoline from the United States.
In a study published in the journal Ambio, scientists found that lead levels in soil in the Northeastern United States had decreased markedly since the introduction of unleaded gasoline.
Many scientists had believed that the lead would stay in soil and snow for a longer period.
The authors of the Ambio study examined samples of the upper layers of soil taken from the same sites of 30 forest floors in New England, New York and Pennsylvania in 1980 and in 1990. The forest environment processed and redistributed the lead faster than the scientists had expected.
Scientists say both studies demonstrate that certain parts of the ecosystem (生态系统) respond rapidly to reductions in atmospheric pollution, but that these findings should not be used as a license to pollute.
It can be inferred from the last paragraph that scientists （）A、are puzzled by the mystery of forest pollutionB、feel relieved by the use of unleaded gasolineC、still consider lead pollution a problemD、lack sufficient means to combat lead pollution
考题
Questions 21 to 25 are based on the following passage.
Lead deposits, which accumulated in soil and snow during the 1960’s and 70’s, were primarily the result of leaded gasoline emissions originating in the United States. In the twenty years that the Clean Air Act has mandated unleaded gas use in the United States, the lead accumulation worldwide has decreased significantly.
A study published recently in the journal Nature shows that air-borne leaded gas emissions from the United States were the leading contributor to the high concentration of lead in the snow in Greenland. The new study is a result of the continued research led by Dr. Charles Boutron, an expert on the impact of heavy metals on the environment at the National Center for Scientific Research in France. A study by Dr. Boutron published in 1991 showed that lead levels in arctic (北极的) snow were declining.
In his new study, Dr. Boutron found the ratios of the different forms of lead in the leaded gasoline used in the United States were different from the ratios of European, Asian and Canadian gasolines and thus enabled scientists to differentiate (区分) the lead sources. The dominant lead ratio found in Greenland snow matched that found in gasoline from the United States.
In a study published in the journal Ambio, scientists found that lead levels in soil in the Northeastern United States had decreased markedly since the introduction of unleaded gasoline.
Many scientists had believed that the lead would stay in soil and snow for a longer period.
The authors of the Ambio study examined samples of the upper layers of soil taken from the same sites of 30 forest floors in New England, New York and Pennsylvania in 1980 and in 1990. The forest environment processed and redistributed the lead faster than the scientists had expected.
Scientists say both studies demonstrate that certain parts of the ecosystem (生态系统) respond rapidly to reductions in atmospheric pollution, but that these findings should not be used as a license to pollute.
The study published in the journal Nature indicates that （）A、the Clean Air Act has not produced the desired resultsB、lead deposits in arctic snow are on the increaseC、lead will stay in soil and snow longer than expectedD、the US is the major source of lead pollution in arctic snow
考题
Questions 21 to 25 are based on the following passage.
Lead deposits, which accumulated in soil and snow during the 1960’s and 70’s, were primarily the result of leaded gasoline emissions originating in the United States. In the twenty years that the Clean Air Act has mandated unleaded gas use in the United States, the lead accumulation worldwide has decreased significantly.
A study published recently in the journal Nature shows that air-borne leaded gas emissions from the United States were the leading contributor to the high concentration of lead in the snow in Greenland. The new study is a result of the continued research led by Dr. Charles Boutron, an expert on the impact of heavy metals on the environment at the National Center for Scientific Research in France. A study by Dr. Boutron published in 1991 showed that lead levels in arctic (北极的) snow were declining.
In his new study, Dr. Boutron found the ratios of the different forms of lead in the leaded gasoline used in the United States were different from the ratios of European, Asian and Canadian gasolines and thus enabled scientists to differentiate (区分) the lead sources. The dominant lead ratio found in Greenland snow matched that found in gasoline from the United States.
In a study published in the journal Ambio, scientists found that lead levels in soil in the Northeastern United States had decreased markedly since the introduction of unleaded gasoline.
Many scientists had believed that the lead would stay in soil and snow for a longer period.
The authors of the Ambio study examined samples of the upper layers of soil taken from the same sites of 30 forest floors in New England, New York and Pennsylvania in 1980 and in 1990. The forest environment processed and redistributed the lead faster than the scientists had expected.
Scientists say both studies demonstrate that certain parts of the ecosystem (生态系统) respond rapidly to reductions in atmospheric pollution, but that these findings should not be used as a license to pollute.
How did scientists discover the source of lead pollution in Greenland? （）A、By analyzing the data published in journals like Nature and Ambio.B、By observing the lead accumulations in different parts of the arctic area.C、By studying the chemical elements of soil and snow in Northeastern America.D、By comparing the chemical compositions of leaded gasoline used in various countries.
考题
Questions 21 to 25 are based on the following passage.
Lead deposits, which accumulated in soil and snow during the 1960’s and 70’s, were primarily the result of leaded gasoline emissions originating in the United States. In the twenty years that the Clean Air Act has mandated unleaded gas use in the United States, the lead accumulation worldwide has decreased significantly.
A study published recently in the journal Nature shows that air-borne leaded gas emissions from the United States were the leading contributor to the high concentration of lead in the snow in Greenland. The new study is a result of the continued research led by Dr. Charles Boutron, an expert on the impact of heavy metals on the environment at the National Center for Scientific Research in France. A study by Dr. Boutron published in 1991 showed that lead levels in arctic (北极的) snow were declining.
In his new study, Dr. Boutron found the ratios of the different forms of lead in the leaded gasoline used in the United States were different from the ratios of European, Asian and Canadian gasolines and thus enabled scientists to differentiate (区分) the lead sources. The dominant lead ratio found in Greenland snow matched that found in gasoline from the United States.
In a study published in the journal Ambio, scientists found that lead levels in soil in the Northeastern United States had decreased markedly since the introduction of unleaded gasoline.
Many scientists had believed that the lead would stay in soil and snow for a longer period.
The authors of the Ambio study examined samples of the upper layers of soil taken from the same sites of 30 forest floors in New England, New York and Pennsylvania in 1980 and in 1990. The forest environment processed and redistributed the lead faster than the scientists had expected.
Scientists say both studies demonstrate that certain parts of the ecosystem (生态系统) respond rapidly to reductions in atmospheric pollution, but that these findings should not be used as a license to pollute.
Lead accumulation worldwide decreased significantly after the use of unleaded gas in the US （）A、was discouragedB、was enforced by lawC、was prohibited by lawD、was introduced
考题
单选题According to the Weather Channel, there is a ______ of rain or even snow in the southwestern region of the United States.A
potentialB
speculationC
chanceD
plan
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单选题After the heavy snow storm many people _____ on the icy streets and injured their arms and legs.A
slippedB
skippedC
skiedD
tripped
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单选题Snow _____ is a big problem in some areas after the snow storm which lasts several days.A
mobilizationB
promotionC
motiveD
removal
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单选题Passage1 Questions 1 to 5 are based on the following passage. It's interesting that the arrival of snow has the effect on people in different countries.(76) For some countries it is an important happening to celebrate each year, while for others a catastrophe （灾害） or even a wonder. But there are countries between these two kinds that normally expect snow some time over the winter months, but never receive snow regularly or in the same quantities every year.Britain is one of them, for which the arrival of snow quite simply creates problems.Within hours of the first snowfalls, however light, roads are blocked; trains and buses have to stop in the middle of the way.Normal communications are affected as well: telephone calls become difficult and the post immediately takes more time than usual.And almost within hours there are also certain shortages-bread, vegetables and other things-not because all these things can no longer be produced or sent to shops,but mainly because people are frightened and go out and store up with food and so on...just for fear that something bad should happen. But why does snow have this effect? After all, the Swiss, the Austrians and the Canadians don't have such problems.It is simply because there is not enough planning and preparation.We need money to buy equipment to deal with snow and ice.To keep the roads clear, for example,requires snow-ploughs (扫雪机) and machines to spread salt.(77) The reason why a country like Britain does not buy snow-ploughs is that they are only used for a few days in any one year, and the money could be more useful in other things such as hospitals, education, helping the old, and so on.3 After a few hours' snowing there are often some shortages of food because______.A
shops have closed downB
people buy as much as they canC
farmers can produce no moreD
people eat more vegetables
考题
单选题The wordstwo kinds in Line 4 mean the countries______.A
which have snow either as yearly happening to celebrate or as rare weatherB
which either have heavy snow or light snowC
to which snow either causes problems or no problemsD
which either have snow-ploughs or no snow-ploughs
考题
单选题According to the writer, Britain is a country______.A
which has regular snowB
which is not well prepared for snowC
for which snow is a catastropheD
for which snow is a wonder
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