题目内容：
Why do some scientists study how plants convert sunlight carbon dioxide, and water into sugars and starches? _______
A．A Because they want algae to produce sugars and starche B．B Because they want green plants to become a new source of energ
C．C Because they want to turn plant sugars to a new form of energ
D．D Because they want to make photosynthesis more efficien
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