题目内容
（请给出正确答案）
Algae under normal conditions in rivers ______ .
A．consume the available nutrients
B．make the oxygen balance
C．force other organisms out of rivers
D．overgrow and die
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更多“Algae under normal conditions …”相关的问题
According to the fifth paragraph, under what conditions are algae able to use solar energy to make hydrogen？ _______A When there is a lot of oxygen in the air.B When there is no oxygen in the air.C When photosynthesis is taking place.D When enough starch is stored.
Which of the statements concerning children's fare is true？
A．Children under two are charged 10% of the normal fare under any circumstances.
B．The second child under two accompanying the same adult is charged 50% of the normal fare.
C．A 12-year-old is charged 50% of the normal fare.
D．Unaccompanied children are charged the normal fare.
Which of the statements concerning children' s fare is true？
A．Children under two are charged 10% of the normal fare under any circumstances.
B．The second child under two accompanying the same adult is charged 50 % of the normal fare.
C．A 12-year-old is charged 50% of the normal fare.
D．Unaccompanied children are charged the normal fare.
A.A. Shipper or his agent can find normal rate in( ).
B.B. TACT Rules
C.C. TACT rates
D.D. contract
E.E. L/C
A．To practice driving with an experienced driver.
B．To drive under normal highway condition.
C．To have the car checked by the license officer.
D．To use it as an identification card.
A．is affected by changes in pressure
B．has a permanent structure
C．forms a free surface
D．is considerably more common
第一篇 Putting Plants to Work
Using the power of the sun is nothing new. People have had solar-powered calculators and buildings with solar panels(太阳能电池板) for decades. But plants are the real experts. They’ve been using sunlight as an energy 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 sugars and starches(淀粉), stored energy that the plants 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 photosynthesis power stations. For example, Maria Ghirardi of the National Renewable Energy Laboratory in Golden. Colo., 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 efficiently 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 photosynthesis, plants normally make sugars or starches. “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 hydrogen 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.”
31 How do plants relate to solar energy？
A They have been using it for billions of years.
B They are the real experts in producing it.
C They have been a source of it.
D They have been used to produce it.
请根据以下内容回答1-5题
Putting Plants to Work
Using the power of the sun is nothing new. People have had solar-powered calculators and buildings with solar panels
for decades. But plants are the real experts: They've been using sunlight as an energy source for billions of years.
Cells in the green leaves of plants work like tiny factories to convert sunlight, carbon dioxide, and water into sugars
and starches, stored energy that the plants can use. This conversion process is called photosynthesis. 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 miniature photosynthetic
power stations. For example, Maria Ghirardi of the National Renewable Energy Laboratory in Golden, Colo.,
is working with green algae. She's trying to trick them into producing hydrogen instead of sugars when they
perform photosynthesis. Once the researchers can get the algae working efficiently, 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 photosynthesis,
plants normally make sugars or starches. “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
hydrogen 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 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 the writer Say about plants concerning solar energy？_______
A Plants are the real experts in producing solar energy.
B Plants have been used to produce solar energy.
C Plants have been using solar energy for billions of years.
D Plants have been a source of solar energy.
A．To find more infections than under normal circumstances.
B．To examine if it is influenza or swine flu.
C．To see if the illness is serious.
D．To stop the illness spread to other areas.
A．She must look after the passengers and do routine work.
B．She must fulfill special duties under all situations.
C．She must remain calm in case of an emergency.
D．She must keep the plane in normal order.
