Once environmental damage(), it takes long time for the ecosystem ( 生态系统 )to recover.
Once environmental damage(), it takes long time for the ecosystem ( 生态系统 )to recover.
A.does
B.is to do
C.has done
D.is done
正确答案:is done
Once environmental damage(), it takes long time for the ecosystem ( 生态系统 )to recover.
A.does
B.is to do
C.has done
D.is done
正确答案:is done
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