表語從句就是放在系統(tǒng)詞后面的從句。例如： It seems as if it were going to rain.似乎要下雨。在這句話里面，seem是系動詞as if引導(dǎo)的就是表語從句。

The question is where we should put it.問題是我們應(yīng)該把它放在哪里。

The question is whether his parents will agree to it.

The reason why he was late is that his bike broke down.