问题
单项选择题
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
答案
参考答案：D
解析：[分析] 结构应用 本句考察的是虚拟语气结构。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。
