1.概念：用作表语的从句叫做表语从句。
2.构成：关联词+简单句
3.引导表语从句的关联词的类型：从属连词that。如：The trouble is that I have lost his
address.麻烦是我把他的地址丢了。从属连词whether,as,as if。如：He looked just as he had looked
ten years before.他看着还与十年前一样。The question is whether they will be able to help
us.问题是他们是不是能帮大家。
注：从属连词if一般不需要来引导表语从句，但as if却可引导表语从句，如：All this was over twenty years ago,but
its as if it was only
yesterday.这都是20多年前的事了，但宛如昨天一样。能跟表语从句的谓语动词一般为系动词be,seem,look等。如：It looked as if
it was going to
rain.看着天要下雨了。连接代词who,whom,whose,what,which,whoever,whatever,whichever 连接副词
wher,when,how,why。如：The problem is who we can get to replace
her.问题是大家能找到哪个去替换她呢。The question is how he did it.问题是他是怎么样做此事的。That was what she
did this morning on reaching the attic.那就是她今晨上了阁楼干的。
讲解：
1.连词because可引导表语从句。如：I think it is because you are doing too
much.我想这是由于你做得太多。
2.在一些表示“建议、劝说、命令”的名词后面的表语从句中，谓语动词用虚拟语气。should+动词原形表示，should可省略。如：My
suggestion is that we start early tomorrow.我的建议是大家明天一早就出发。
