________ is known to all is that effecti

问题选择题

________ is known to all is that effective measures should be taken to deal with the problem of the overexploitation of our resources.

A．What

B．It

C．As

D．Which

答案

答案：A

选A　考查主语从句。分析句子结构可知，空处引导主语从句，且在从句中作主语，所以用what引导。注意区分以下结构：As is known to all, effective measures should be ...，其中As引导非限制性定语从句；It is known to all that effective measures should be ...，其中It为形式主语，真正的主语是that引导的主语从句。