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单选题
Plants use the carbon, along with sunlight, for growth, and （） oxygen into the atmosphere in a process known as photosynthesis.
A
relieve
B
relate
C
release
D
retain
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更多 “单选题Plants use the carbon, along with sunlight, for growth, and （） oxygen into the atmosphere in a process known as photosynthesis.A relieveB relateC releaseD retain” 相关考题
考题
As there is less and less coal and oil, scientists are exploring new ways of making use of ____ energy, such as sunlight, wind and water for power and fuel.A. primary B. alternative C. instant D. unique
考题
They use special chemical substance to _________ the growth of crops.A aggravateB accelerateC strengthenD reinforce
考题
Which statement concerning carbon dioxide is FALSE ________．A.It displaces the oxygen in the airB.It cannot be seenC.It cannot be smelledD.It is safe to use near personnel in a confined space
考题
As there is less and less coal and oil, scientists are exploring new ways of making use of _______ energy, such as sunlight, wind and water for power and fuel.A.primary
B.alternative
C.instant
D.unique
考题
共用题干
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." Researchers find it difficult to make algae produce hydrogen efficiently because_______________.A:it is hard to create an airfree environmentB:it is expensive to remove the sulfate from the environmentC:removing the sulfate slows down hydrogen productionD:the algae's cells work slowly if there is no oxygen in the air
考题
共用题干
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." Algae are able to use solar energy to produce hydrogen when_______________.A:they are grown in narrow-necked bottlesB:there is no oxygen in the airC:there is enough oxygen in the airD:enough starch is stored
考题
Soil is the surface layer of the Earth that nourishes and supports the growth of rooted plants.A: accepts
B:arranges
C:feeds
D:shelters
考题
共用题干
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
考题
共用题干
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." What does Ghirardi say about algae?A:They can be a good energy source.B:They grow faster in a reactor.C:They will be planted everywhere.D:They are cheap to eat.
考题
共用题干
第一篇Plant GasScientists have been studying natural sources of methane（甲烷，沼气）for decades but hadn't regarded plants as a producer, notes Frank Keppler, a geochemist（地球化学家）at the Max Planck Institute for Nuclear Physics in Heldelberg,Germany. Now Keppler and his colleagues find that plants,from grasses to trees,may also be sources of the greenhouse gas.This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.Previously,researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes（微生物）need to be in environments without oxygen to produce methane.Methane is a greenhouse gas, like carbon dioxide.Gases such as methane and carbon dioxide trap heat in Earth's atmosphere and contribute to global warming.In its experiments, Keppler's team used sealed chambers（室，房间；腔）that contained the same concentration of oxygen that Earth's atmosphere has.They measured the amounts of methane that were released by both living plants and dried plant material,such as fallen leaves.With the dried plants,the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C.At 30 degrees C.,they found,a gram of dried plant material released up to 3 nanograms（微克）of methane per hour(One nanogram is a millionth of a gram). With every 10-degree rise in temperature,the amount of methane released each hour roughly doubled.Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight.Because there was plenty of oxygen available,it's unlikely that the types of bacteria(bacterium的复数，细菌）that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions.That's another strong sign that the gas came from the plants and not soil microbes.The new finding is an"interesting observation,"says Jennifer Y. King,a biogeochemist（生物地球化学家）at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane,they may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plant's influence,she notes.Which of the following about methane is not mentioned in the passage?A:Plants growing in soil release methane.B:Plants growing in water release methane.C:Soil microbes consume methane.D:Microbes in plants produce methane.
考题
共用题干
第一篇Plant GasScientists have been studying natural sources of methane（甲烷，沼气）for decades but hadn't regarded plants as a producer, notes Frank Keppler, a geochemist（地球化学家）at the Max Planck Institute for Nuclear Physics in Heldelberg,Germany. Now Keppler and his colleagues find that plants,from grasses to trees,may also be sources of the greenhouse gas.This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.Previously,researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes（微生物）need to be in environments without oxygen to produce methane.Methane is a greenhouse gas, like carbon dioxide.Gases such as methane and carbon dioxide trap heat in Earth's atmosphere and contribute to global warming.In its experiments, Keppler's team used sealed chambers（室，房间；腔）that contained the same concentration of oxygen that Earth's atmosphere has.They measured the amounts of methane that were released by both living plants and dried plant material,such as fallen leaves.With the dried plants,the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C.At 30 degrees C.,they found,a gram of dried plant material released up to 3 nanograms（微克）of methane per hour(One nanogram is a millionth of a gram). With every 10-degree rise in temperature,the amount of methane released each hour roughly doubled.Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight.Because there was plenty of oxygen available,it's unlikely that the types of bacteria(bacterium的复数，细菌）that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions.That's another strong sign that the gas came from the plants and not soil microbes.The new finding is an"interesting observation,"says Jennifer Y. King,a biogeochemist（生物地球化学家）at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane,they may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plant's influence,she notes.Which statement is true of the methane emissions of plants in the experiment?A:The lower the temperature,the higher the amount of methane emissions.B:Living plants release less methane than dried plants at the same temperature.C:When exposed to sunlight,plants stop releasing methane.D:The higher the temperature,the greater the amount of methane emissions.
考题
共用题干
第一篇Plant GasScientists have been studying natural sources of methane（甲烷，沼气）for decades but hadn't regarded plants as a producer, notes Frank Keppler, a geochemist（地球化学家）at the Max Planck Institute for Nuclear Physics in Heldelberg,Germany. Now Keppler and his colleagues find that plants,from grasses to trees,may also be sources of the greenhouse gas.This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.Previously,researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes（微生物）need to be in environments without oxygen to produce methane.Methane is a greenhouse gas, like carbon dioxide.Gases such as methane and carbon dioxide trap heat in Earth's atmosphere and contribute to global warming.In its experiments, Keppler's team used sealed chambers（室，房间；腔）that contained the same concentration of oxygen that Earth's atmosphere has.They measured the amounts of methane that were released by both living plants and dried plant material,such as fallen leaves.With the dried plants,the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C.At 30 degrees C.,they found,a gram of dried plant material released up to 3 nanograms（微克）of methane per hour(One nanogram is a millionth of a gram). With every 10-degree rise in temperature,the amount of methane released each hour roughly doubled.Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight.Because there was plenty of oxygen available,it's unlikely that the types of bacteria(bacterium的复数，细菌）that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions.That's another strong sign that the gas came from the plants and not soil microbes.The new finding is an"interesting observation,"says Jennifer Y. King,a biogeochemist（生物地球化学家）at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane,they may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plant's influence,she notes.To test whether plants are a source of methane,the scientists created_______.A:an oxygen-free environmentB:an environment with the same concentration of oxygen as the Earth hasC:a carbon dioxide-free environmentD:an environment filled with the greenhouse gas
考题
An Essential Scientific Process
All life on the earth depends upon green plants. Using sunlight, theplants produce their own food. Then animals feed upon the plants. They take inthe nutrients the plants have made sted. But that’s not all.Sunlight also helps a plant produce oxygen. Some of the oxygen is used by theplant, but a plant usually produces me oxygen than it uses. The excess oxygenis necessary f animals other ganisms to live.
The process of changing light into food oxygen is calledphotosynthesis. Besides light energy from the sun, plants also use water carbon dioxide. The water gets to the plant through its roots. The carbondioxide enters the leaves through tiny openings called stomata. The carbondioxide travels to chloplasts, special cells in the bodies of green plants.This is photosynthesis takes place. Chloplasts contain the chlophyllsthat give plants their green col. The chlophylls are the molecules thattrap light energy. The trapped light energy changes water carbon dioxide toproduce oxygen a simple sugar called glucose.
Carbon dioxide oxygen move into out of the stomata. Watervap also moves out of the stomata. Me than 90 percent of water a planttakes in through its roots escapes through the stomata. During the daytime, thestomata of most plants are open. This allows carbon dioxide to enter the leavesf photosynthesis. As night falls, carbon dioxide is not needed. The stomataof most plants close. Water loss stops.
If photosynthesis ceased, there would be little food other ganicmatter on the earth. Most ganisms would disappear. The earth’s atmospherewould no longer contain oxygen. Photosynthesis is essential f life on ourplanet.
词汇：
nutrient n.营养物
ganism n.生物体，有机体
carbon dioxide n.二氧化碳
chloplast n.叶绿体
molecule n.分子
vap n.水蒸气
oxygen n.氧气
photosynthesis n.光合作用
chlophyll n.叶绿素
glucose n.葡萄糖
cease v.停止
注释：
1.Then animals feed upon the plants.动物以植物为食。
练习：
5.Another good title f this passage would be
A.Oxygen Carbon Dioxide.
B.Plants Their Roots.
C.How Photosynthesis Wks.
D.Why Our Earth Needs Water.
考题
An Essential Scientific Process
All life on the earth depends upon green plants. Using sunlight, theplants produce their own food. Then animals feed upon the plants. They take inthe nutrients the plants have made sted. But that’s not all.Sunlight also helps a plant produce oxygen. Some of the oxygen is used by theplant, but a plant usually produces me oxygen than it uses. The excess oxygenis necessary f animals other ganisms to live.
The process of changing light into food oxygen is calledphotosynthesis. Besides light energy from the sun, plants also use water carbon dioxide. The water gets to the plant through its roots. The carbondioxide enters the leaves through tiny openings called stomata. The carbondioxide travels to chloplasts, special cells in the bodies of green plants.This is photosynthesis takes place. Chloplasts contain the chlophyllsthat give plants their green col. The chlophylls are the molecules thattrap light energy. The trapped light energy changes water carbon dioxide toproduce oxygen a simple sugar called glucose.
Carbon dioxide oxygen move into out of the stomata. Watervap also moves out of the stomata. Me than 90 percent of water a planttakes in through its roots escapes through the stomata. During the daytime, thestomata of most plants are open. This allows carbon dioxide to enter the leavesf photosynthesis. As night falls, carbon dioxide is not needed. The stomataof most plants close. Water loss stops.
If photosynthesis ceased, there would be little food other ganicmatter on the earth. Most ganisms would disappear. The earth’s atmospherewould no longer contain oxygen. Photosynthesis is essential f life on ourplanet.
词汇：
nutrient n.营养物
ganism n.生物体，有机体
carbon dioxide n.二氧化碳
chloplast n.叶绿体
molecule n.分子
vap n.水蒸气
oxygen n.氧气
photosynthesis n.光合作用
chlophyll n.叶绿素
glucose n.葡萄糖
cease v.停止
注释：
1.Then animals feed upon the plants.动物以植物为食。
练习：
4.This passage is primarily developed by
A.explaining a process.
B.telling a sty.
C.comparing contrasting.
D.convincing the reader of plants’ imptance.
考题
An Essential Scientific Process
All life on the earth depends upon green plants. Using sunlight, theplants produce their own food. Then animals feed upon the plants. They take inthe nutrients the plants have made sted. But that’s not all.Sunlight also helps a plant produce oxygen. Some of the oxygen is used by theplant, but a plant usually produces me oxygen than it uses. The excess oxygenis necessary f animals other ganisms to live.
The process of changing light into food oxygen is calledphotosynthesis. Besides light energy from the sun, plants also use water carbon dioxide. The water gets to the plant through its roots. The carbondioxide enters the leaves through tiny openings called stomata. The carbondioxide travels to chloplasts, special cells in the bodies of green plants.This is photosynthesis takes place. Chloplasts contain the chlophyllsthat give plants their green col. The chlophylls are the molecules thattrap light energy. The trapped light energy changes water carbon dioxide toproduce oxygen a simple sugar called glucose.
Carbon dioxide oxygen move into out of the stomata. Watervap also moves out of the stomata. Me than 90 percent of water a planttakes in through its roots escapes through the stomata. During the daytime, thestomata of most plants are open. This allows carbon dioxide to enter the leavesf photosynthesis. As night falls, carbon dioxide is not needed. The stomataof most plants close. Water loss stops.
If photosynthesis ceased, there would be little food other ganicmatter on the earth. Most ganisms would disappear. The earth’s atmospherewould no longer contain oxygen. Photosynthesis is essential f life on ourplanet.
词汇：
nutrient n.营养物
ganism n.生物体，有机体
carbon dioxide n.二氧化碳
chloplast n.叶绿体
molecule n.分子
vap n.水蒸气
oxygen n.氧气
photosynthesis n.光合作用
chlophyll n.叶绿素
glucose n.葡萄糖
cease v.停止
注释：
1.Then animals feed upon the plants.动物以植物为食。
练习：
1.In the first paragraph，the wd “excess” means
A.heavy.
B.extra.
C.green.
D.liquid.
考题
An Essential Scientific Process
All life on the earth depends upon green plants. Using sunlight, theplants produce their own food. Then animals feed upon the plants. They take inthe nutrients the plants have made sted. But that’s not all.Sunlight also helps a plant produce oxygen. Some of the oxygen is used by theplant, but a plant usually produces me oxygen than it uses. The excess oxygenis necessary f animals other ganisms to live.
The process of changing light into food oxygen is calledphotosynthesis. Besides light energy from the sun, plants also use water carbon dioxide. The water gets to the plant through its roots. The carbondioxide enters the leaves through tiny openings called stomata. The carbondioxide travels to chloplasts, special cells in the bodies of green plants.This is photosynthesis takes place. Chloplasts contain the chlophyllsthat give plants their green col. The chlophylls are the molecules thattrap light energy. The trapped light energy changes water carbon dioxide toproduce oxygen a simple sugar called glucose.
Carbon dioxide oxygen move into out of the stomata. Watervap also moves out of the stomata. Me than 90 percent of water a planttakes in through its roots escapes through the stomata. During the daytime, thestomata of most plants are open. This allows carbon dioxide to enter the leavesf photosynthesis. As night falls, carbon dioxide is not needed. The stomataof most plants close. Water loss stops.
If photosynthesis ceased, there would be little food other ganicmatter on the earth. Most ganisms would disappear. The earth’s atmospherewould no longer contain oxygen. Photosynthesis is essential f life on ourplanet.
词汇：
nutrient n.营养物
ganism n.生物体，有机体
carbon dioxide n.二氧化碳
chloplast n.叶绿体
molecule n.分子
vap n.水蒸气
oxygen n.氧气
photosynthesis n.光合作用
chlophyll n.叶绿素
glucose n.葡萄糖
cease v.停止
注释：
1.Then animals feed upon the plants.动物以植物为食。
练习：
2.Which of the following does not move through a plant’s stomata?
A.Carbon dioxide.
B.Water vap.
C.Oxygen.
D.Food.
考题
单选题Which extinguishing agent is recommended in the Chemical Data Guide for use on a carbon disulfide fire?（）A
Alcohol foamB
Dry chemicalC
Chemical foamD
Water fog
考题
单选题A land ethic of course cannot prevent the conversion, management, and use of the resources of soil, waters, plants and animals.A
altercation B
alternation C
alteration D
allocation
考题
单选题Dozens of scientific groups all over the world have been _____ the goal of a practical and economic way to use sunlight to split water molecules.A
pursuingB
chasingC
reachingD
winning
考题
单选题When required to work where there may be explosive gases, you should use tools which are （）A
approved by the Coast GuardB
high carbon steelC
fixed with a ferrous coverD
nonsparking
考题
单选题The farmers know that fertilizer can accelerate the growth of these tomato plants.A
accommodate B
accord C
quicken D
accomplish
考题
问答题Practice 1 Genetic researchers have accelerated a plant’s growth by making its cells split faster—a technique that could someday lead to healthier crops, shorter growing seasons and less use of herbicides. One outside scientist called the findings astonishing. But the technique needs more testing on a range of plants, and public fear of genetically modified food is jeopardizing support for such experiments, especially in Europe, researchers said. The experiment, reported Thursday in the journal Nature, was carried out by a team at Cambridge University. The researchers first took a gene promoting cell division from inside the Arabidopsis plant, a flowering weed often used for genetic experiments. They transplanted that gene into a tobacco plant. There, in an especially potent form, the gene produced large amounts of a protein that, in combination with other chemicals naturally in the tobacco, made the plant’s cells divide more quickly at the tips of roots and shoots. Within a month after planting, the altered tobacco grew as much as twice as tall as other tobacco plants. Ultimately, the other plants caught up, and both groups then appeared identical in all ways. “It’s sort of like they’ve been able to make the plant go full throttle,” a said plant growth biologist John Schiefelbein at the University of Michigan. The leader of the study, Claire Cockcroft, said it is conceivable that the technique could be transferred to other species. Such plants, which probably would take years to develop commercially, might allow an extra planting in some climates or the introduction of crops in places where the growing season is too short, researchers said. The quick-growth plants would presumably take hold more easily, requiring less chemical herbicide to knock out weeds. Such plants might make easier and cheaper sources of some drugs. In scientific circles, the British research may also help settle an intense debate over what makes plants grow. Some argue, like these researchers, that something at the cellular level switches on growth; others look to hormones or other chemicals at a higher level of the plant’s makeup. “This is astonishing. Normally you would expect growth regulation to be more complicated,” said plant researcher Xuemin Wang at Kansas State University. “This has huge implications in terms of how we look at plant growth.” Biotechnology companies have genetically manipulated fruits and vegetables to make them more attractive or resistant to insects and disease. Genetic work has shown some early promise for faster growth, too. But previous attempts to boost growth through faster cell division have produced more cells—but smaller ones—and no overall growth. Scientists said such work is safe, with little chance of accidentally turning an unwanted plant into a fast-growing weed. After all, crops have been selectively bred for decades to bring out certain traits. However, ethicist Jeffrey Burkhardt at the University of Florida’s Institute of Food and Agricultural Sciences said selective breeding takes perhaps 15 years, giving scientists ample time to see the implications. “With the new biotechnology, you’re potentially moving traits in and out within a year,” he said.
考题
单选题Fertilizer will（）the growth of these tomato plants.A
accomplishB
accelerateC
accumulateD
account
考题
单选题The best tool to use for removing the carbon ridge at the top of an enginecylinder, prior to removing the piston, is to use（）A
an electric grinderB
a metal scraperC
a reamerD
a three-wing hone
考题
单选题In order to remove the carbon deposit from the threaded recess, we can use（）A
a driverB
a scraperC
a tapD
a file
考题
单选题A number of biological sewage treatments plants are in use at sea but nearly all work on the principle called （）A
deoxygenatingB
extended aerationC
oxygenatingD
bubbling air
考题
单选题What is the fourth paragraph of the passage mainly about?A
The ways to use solar power.B
The advantages of solar power.C
The places to build the solar power plants.D
The difficulties of putting solar power to use widely.
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