单项选择题

Once environmental damage（）, it takes many years for the system to recover.

A. has done
B. is to do
C. does
D. is done

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So little（）about physics that the lecture was completely beyond me.

A. I knew
B. did I know
C. I had known
D. had I known
单项选择题
There is no evidence（）oil price will come down in the near future.

A、which
C、where
B、that
D、as
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