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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单项选择题
I don't think Frank is ______ engineer as Bill.
A．as able an
B．able as an
C．as an able
D．an as able
单项选择题
It does no good ______ anything at such times.
A．saying
B．to say
C．being said
D．to saying
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