四、应注意的问题：1. 连系动词be，appear，seem，look等之后可以跟表语从句。It was because he didn't pass the exam. 那是因为他没有通过考试。It seems(that)he was late for the train. 看来他没搭上火车。It appears that she was wrong. 看来她错了。It seems to me that we should answer for this. 在我看来，我们似乎应该对此事负责。It appears to her that he wants to teach us all he has. 在她看来，他似乎要把他所会的都教给我们。2. 引导表语从句的引导词有以下几类。1)wh-疑问词My question is who left. 我想问的是谁离开了。 That's what he wants. 那是他想要的。What I wonder is when he left. 我想知道他是何时离开的。This is where they once lived. 这就是他们曾经住过的地方。That is why he didn't come here. 这就是他为何没到这儿来的原因。2)whether My question is whether he left(or not). 我的问题是他是否离开了。 注：if不能引导表语从句。3)that The fact is that he left. 事实是他离开了。The truth is(that)I didn't go there. 事实是我没去那儿。 注：引导表语从句的连词that间或可以省略。4)because，as，as if，as though It's just because he doesn't know her. 这是仅仅因为他不认识她。Things are not always as they seem to be. 事物并不总是如其表象。

He looks as if he's tired. 他好像累了