问题
选择题
Before a problem can be solved, it must be obvious ______the problem itself is.
A．what
B．that
C．which
D．why
答案
答案：A
题目分析：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。