单项选择题

A new technique ______ , the yields as a whole increased by 20 percent.

A. working out

B. having worked out
C. having been worked out

D. to have been worked out

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单项选择题

If we continue to ignore the issue of global warming, we will almost certainly suffer the ______ effects of climatic changes worldwide.

A. dubious
B. drastic
C. trivial
D. toxic

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