A Because they want algae to produce sugars and starches.
B Because they want green plants to become a new source of energy.
C Because they want to turn plant sugars to a new form of energy.
D Because they want to make photosynthesis more efficient.
38. 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.
39. Researchers have met with difficulties when trying to make algae produce hydrogen efficiently. Which one of the following is one such difficulty?
A It is not possible to remove sulfate from the environment.
B It is not possible to work in an airfree environment to produce hydrogen.
C It is not easy to make sugars instead of hydrogen.
D It is too slow for algae to produce hydrogen when the sulfate is removed.
40. What is NOT true of algae?
A They are easy to grow.
B They can be a very good fuel source.
C They are cheap to eat.
D They can be used in many ways.
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