单项选择题

If the () of carbon dioxide in the atmosphere is increased as a result of air pollution.

A. rate
B. proportion
C. extent
D. amount
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He () polite at the party last night. But actually she is not the least bit polite.
A. was being
B. was
C. should be
D. were
单项选择题
( )from outer space, our earth looks like a blue water ball.
A. Seen
B. Seeing
C. To see
D. See
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