单项选择题

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

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

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单项选择题

The law requires that everyone（）his car checked at least once a year.

A．has
B．had
C．have
D．must have

单项选择题

The news（）he had landed on the moon spread all over the school campus.

A．which
B．that
C．what
D．as

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