Question

Before a problem can be solved, it must be obvious ______the problem itself is.

A．what

B．that

C．which

D．why

Answer 1

A

试题分析：考查主语从句：句意：在问题解决之前，问题本身是什么必须明确。it在句中做形式主语，真正的主语是what the problem itself is ，what在主语从句中做表语，选A。