单选题
The human beings have polluted the environment seriously. It is time the United Nations
must take
some measures.
A、
take
B、
taking
C、
to take
D、
took
【正确答案】
D
【答案解析】
[解析] It is (about/high) time that...句型用虚拟语气，其谓语部分用一般过去时，因此D为答案。
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