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29． Why are green plants and grass helpful?
A． Because they can hold the water．
B． Because they can stop the wind from blowing the earth away．
C． Because they can keep the earth wet．
D．All the above．
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更多 “ 29． Why are green plants and grass helpful?A． Because they can hold the water．B． Because they can stop the wind from blowing the earth away．C． Because they can keep the earth wet．D．All the above． ” 相关考题
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第一篇Putting Plants to WorkUsing the power of the sun is nothing new.People have had solar-powered calculators and buildings withsolar panels（太阳能电池板）for decades. But plants are the real experts. They' ve been using sunlight as anenergy source for billions of years.Cells in the green leaves of plants work like tiny factories to convert sunlight, carbon dioxide（二氧化 碳）,and water into sugarsand starche（淀粉）,stored energy that the piants can use. This conversion process is called photosynthesis (光合作用）Unfortunately, unless you' re a plant, it's difficult and expensive to convert sunlight into storable energy. That's why scientists are taking a closer look at exactly how plants do it.Some scientists are trying to get plants,or biological cells that act like plants, to work as very small photosynthesic power stations. For example, Maria Ghirardi of the National Renewable Energy Laboratory in Golden. Cobo.,is working with green algae（水藻）.She's trying to trick them into producing hydrogen instead of sugars when they perform photosynthesis. Once the researchers can get the algae working efficient- ly ,the hydrogen that they produce could be used to power fuel cells in cars or to generate electricity.The algae are grown in narrow-necked glass bottles to produce hydrogen in the lab. During photosynthe- sis , plants normally make sugars or strchds. "But under certain conditions,a lot of algae are able to use the sunlight energy not to store starch , but to make hydrogen."Ghirardi says. For example ,algae will produce hy-drogen in an airfree environment. It' s the oxygen in the air that prevents algae from making hydrogen most of the time.Working in an airfree environment, however, is difficult. It's not a practical way to produce cheap energy. But Ghirardi and her colleagues have discovered that by removing a chemical called sulfate（硫酸盐） from the environment that the algae grow in, they will make hydrogen instead of sugars,even when air is present.Unfortunately, removing the sulfate also makes the algae's cells work very slowly,and not much hydrogen is produced. Still ,the researchers see this as a first step in their goal to produce hydrogen efficiently from algae. With more work,they may be able to speed the cells' activity and produce larger quantities of hydrogen.The researchers hope that algae will one day be an easy-to-use fuel source. The organisms are cheap to get and to feed, Ghirardi says,and they can grow almost anywhere:"You can grow them in a reactor, in a pond. You can grow them in the ocean. There's a lot of flexibility in how you can use these organisms." Scientists study how photosynthesis works because they want to_______________.A: improve the efficiency of itB: turn plant sugars to a new form of energyC: get more sugars and starches from plantsD: make green plants a new source of energy
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We Need Green SpaceDecades ago,any open field,any vacant lot,any group of trees were the places where children played.As families left family farms,small towns,and the countryside,and moved into cities,the places for their children to play in became rarer.(46)_________In fact,all people's lives change a lot when they move to the city. In cities,homes are built on top of one another in enormous apartment buildings.The feeling of private space and ownership no longer exists in houses literally piled one on the other.Psychologists have been studying the changes people experience when they leave rural areas and move into urban environments.(47)________Children can play on paved playgrounds.That's true.(48)_________Without grass and trees and bushes and,yes,dirt and mud to get dirty in, children miss an important part of childhood.The human soul,it seems,needs to stay close to its roots.Adults can plant lots of things like bulbs in window boxes and large containers.(49)_________ The lack of green space is now recognized and understood as a problem.City planners一the people who design neighborhoods一have begun to work on a solution.They want to build more parks,but land in cities is quite costly.So they look for land that no one else wants.Along rivers,under power lines,near ditches and highways—(50)________Why not use these unused spaces for green areas?Neighborhood groups have coordinated their efforts to clean up the trash or garbage.Soil from new building projects in the city has been trucked by lorries into these areas.This soil has been dumped along the sides of rivers,and strong walls have been erected to hold it there.Trees and bushes have been planted;the roots of these plants will hold the soil, too,and the green leaves make the area beautiful.________（49）A:However,they just don't have as much fun as children in small towns.B:Children in the cities had few options,fewer choices of places to play.C:Why is there no place children in cities to play?D:One clear finding from their studies is that people need green spaces for better mental health.E:However,tending window boxes isn't the same as being an amateur gardener and growing peas,tomatoes and salad greens in a backyard garden.F:these are the spaces that no one uses and they are everywhere.
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Green Energy1.Green energy is energy that is produced in a manner that has, less of a negative impact to the environment than energy sources like fossil fuels,which are often produced with harmful side effects."Greener" types of energy that often come to mind are solar,wind,geothermal and hydro energy.There are several more,even including nuclear energy,that is sometimes considered a green energy source because of its lower waste output relative to energy sources such as coal or oil.2.The goal of green energy is generally to create power with as little pollution as possible produced as a by-product. Every form of energy collection will result in some pollution,but those that are green are known to cause less than those that are not. Most people who advocate greener sources of energy claim that the result of worldwide use of green energy will result in the ability to preserve the planet for a longer time.Greenhouse gases,a by-product of traditional sources of energy such as fossil fuels are thought to be causing global warming,or the process of the Earth heating up at an accelerated pace.3.It is not completely necessary for green energy sources to come from places like solar or wind fields,which are examples of green"power plants".A green energy source can be a building that is designed in a way that it keeps itself cool in the daytime and heated in the night through its architectural design rather than having an air-conditioning or a heating system. The conservation of energy through architectural（建筑学的）design becomes, itself, a green energy source. Similarly, many sources of green energy can come directly from the area in which the energy is needed rather than from an outside source.4.One of the goals of green energy technology is to take existing fossil fuel energy technology and clean it up so it is produced more cleanly. One such case is that of clean coal technology,where scientists are trying to find ways to extract energy from coal and other fossil fuels without all of the harmful side effects.The success of such these types of green energy depend upon the ability to extract harmful by-products from fossil fuels while not only being energy efficient,but by being cost efficient as well.Paragraph 3______A:Why Do We Develop Green Energy?B:What Is the Goal of Green Energy?C:What Is the Weakness of Green Energy?D:What Is a Green Energy?E:How Much Does the Green Energy Cost Every Year?F: How Many Kinds of Green Energy We Can Take Use of?
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共用题干
Green Energy1.Green energy is energy that is produced in a manner that has, less of a negative impact to the environment than energy sources like fossil fuels,which are often produced with harmful side effects."Greener" types of energy that often come to mind are solar,wind,geothermal and hydro energy.There are several more,even including nuclear energy,that is sometimes considered a green energy source because of its lower waste output relative to energy sources such as coal or oil.2.The goal of green energy is generally to create power with as little pollution as possible produced as a by-product. Every form of energy collection will result in some pollution,but those that are green are known to cause less than those that are not. Most people who advocate greener sources of energy claim that the result of worldwide use of green energy will result in the ability to preserve the planet for a longer time.Greenhouse gases,a by-product of traditional sources of energy such as fossil fuels are thought to be causing global warming,or the process of the Earth heating up at an accelerated pace.3.It is not completely necessary for green energy sources to come from places like solar or wind fields,which are examples of green"power plants".A green energy source can be a building that is designed in a way that it keeps itself cool in the daytime and heated in the night through its architectural design rather than having an air-conditioning or a heating system. The conservation of energy through architectural（建筑学的）design becomes, itself, a green energy source. Similarly, many sources of green energy can come directly from the area in which the energy is needed rather than from an outside source.4.One of the goals of green energy technology is to take existing fossil fuel energy technology and clean it up so it is produced more cleanly. One such case is that of clean coal technology,where scientists are trying to find ways to extract energy from coal and other fossil fuels without all of the harmful side effects.The success of such these types of green energy depend upon the ability to extract harmful by-products from fossil fuels while not only being energy efficient,but by being cost efficient as well.Nuclear energy is sometimes considered a green energy source because of its______.A:global warmingB:carbon emissionC:lower waste outputD:a green energy sourceE:fossil fuels F: clean fuels
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Why is QoS important in a converged network?（）A、Because data does not need to arrive intact, so data transfer rates can be variableB、Because lost voice-data packets must be retransmittedC、Because voice data packets should arrive quickly and sequentially, and with no lost dataD、Because voice data packets must follow a single dedicated path through the network
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单选题Why do some people get sick after drinking the water from the river?A
Because the river is pollutedB
Because the river makes the earth more beautifulC
Because the river can only offer water to animalsD
Because there are too many animals and plants in the river
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单选题Why do students like the self-protection lesson?①Because there are no tests.②Because the lessons are boring.③Because they can learn how to save lives.④Because they can know how to stop danger before it happens.A
①②B
②③C
①②④D
①③④
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单选题Why switch grass and Miscanthus were taken as energy plant?A
Because they contain more cellulose.B
Because genomes have been sequenced for clues to make other plants better energy crops.C
Because some scientists are breeding a wide variety o[Candidate crops.D
Because the spotlight is on this underdeveloped field.
考题
单选题When making landfall at night，you can determine if a light is a major light or an offshore buoy by（）.A
the intensity of the lightB
checking the period and characteristics against the Light ListC
the color，because the buoy will have only a red or a green lightD
Any of the above can be used to identify the light
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