表语从用法1
定义：用作表语的从句叫做表语从句2
引导表语的从句的关联词的种类（1）从属连词 that
The trouble is that I have lost his address
The reason was that he was late for school
(2）从属连词 whether， as, as if He looked just as he had lookedten years before
The question is whether they will be able to help us
注:从属连词 if 一般不用来引导表语从句,但 as if 却可引导表语从句
All this was over twenty years ago, but it’s as if it was only yesterday
The key is whether we can solve the problem
It looked as if it was going to rain
注：能跟表语从句的谓语动词一般为系动词 be, seem, look， sound等He looked just as he had looked ten years before
It sounds as if someone is knocking at the door
（ 3) 连 接 代 词 who ， whom ， whose, what, which ， whoever ， whatever， whichever 在表语从句中做主语、宾语等
The problem is who we can get to replace her
That was what she did this morning on reaching the agreement
