题目内容

Campaigns began in the early 1980s, when people___the negative effects of CO2 emission.

A. realize
B. realized
C. have realized
D. had realized

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Do you know what___so much greenhouse gases in the air？

A. producing
B. has produced
C. will produce
D. produces

The environment on this planet is worsening, for few people___measures to protect it

A. takes
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A. interview
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A. may
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