What is the main function of cyanobacteria？
A. To make more dust storms.
B. To keep the soil flying.
C. To keep the soil to the ground.
D. To create more rocks.
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听力原文：W: George, where were you yesterday evening？ I expected to see you at the concert.
M: Oh, I waited for you at the comer of Thomas Street. Then I looked for you at your flat, but the house keeper said you were out.
Q: Why didn't they meet that evening？
(14)
A. They waited for each other at different concerts.
B. They waited for each other at different places.
C. They went to the street corner at different times.
D. The man went to the concert but the woman didn't.
The earth is unfrozen today with the appearance of ______.
A. the methane blanket
B. a mile-thick layer of ice
C. new life forms
D. the carbon dioxide
The photosynthesis by ancient microbes is an example of ______.
A. the change of Earth
B. the long history of Earth
C. the life's influences on Earth
D. the power of sunlight
According to Edwards, the microbes are now ______.
A. recognized by most people
B. neglected by most people
C. died out from the Earth
D. out of action of the Earth system
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