1. Before a problem can be solved, it must be obvious ______ the problem itself is. (2011·湖南卷31)
A. what B. that
C. which D. why
【解析】选A。空白处后句子缺表语。因此不能选B。B中的that 只起引导作用，无实意。而该句选what既起了引导作用，又作了句子成分表语。
2. It is still under discussion ______ the old bus station should be replaced with a modern hotel or not. (2011·重庆卷22)
A. whether B. when
C. which D. where
