Question

________ 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

Answer 1

A

選A　考查主語從句。分析句子結(jié)構(gòu)可知，空處引導主語從句，且在從句中作主語，所以用what引導。注意區(qū)分以下結(jié)構(gòu)：As is known to all, effective measures should be ...，其中As引導非限制性定語從句；It is known to all that effective measures should be ...，其中It為形式主語，真正的主語是that引導的主語從句。