二、引导词：
连词 that /whether/as if /as though/because
连接代词what / who /whom/which/whose/whatever/whoever/whomever/
whichever
连接副词 when / where/ why /how
1．由连词that，whether引导的表语从句。主句的主语常常是抽象名词，如question(问题)，trouble(麻烦)，problem(问题)，result(结果)，chance(可能性)，suggestion(建议)，idea(想法)，reason(理由)等。表语从句对主句主语进行说明、解释，使主语的内容具体化。
The trouble is (that) he has lost his money.
麻烦的事是他丢了钱。
The question is whether we need more ice cream.
问题是我们是否还需要更多的冰淇淋。
The problem was that it was too valuable for everyday use.
问题是它作为日常之用太贵重了。
