一般情況下，表語從句的that 是不能省略的。如:
1、This is what I want.
這就是我想要的。
2、The reason why he was late is that his bike broke down.
他遲到是因為腳踏車壞了。
3、Next sunday is when we shall meet.
下週日是我們見面的時間。
4、This is why I am late.
這就是我遲到的原因。
5、My problem is which computer to choose.
我的問題是不知道選哪個電腦好。
但是，在下列情況下，表語從句做that 是可以省略的;
1、當主句中含動詞do的某種形式時，that可以省略。如：
What I want to do is (that) I can go up to him and thank him. 我想做的事是走到身邊去感謝他。
2、當句子的主語是：
advice, demand, decision, desire, idea, insistence, instruction, order, plan, proposal, recommendation, request, requirement, suggestion, wish等名詞時，表語從句須用虛擬語氣，即：should +do。如：
My advice is that you should go to apologize to him. 我的建議是你應該去向他道歉。
此外，除that 外，連線表語從句的連線詞還有： what, who, when, where, which, why, whether, how, whoever，whichever ，whatever等。還有如because, as if, as though等。
1、His suggestion is that we should stay calm.
他的建議是，我們應該保持冷靜。
2、The question is when he can arrive at the hotel.
問題是，他什麼時候可以到達酒店。
一般情況下，表語從句的that 是不能省略的。如:
1、This is what I want.
這就是我想要的。
2、The reason why he was late is that his bike broke down.
他遲到是因為腳踏車壞了。
3、Next sunday is when we shall meet.
下週日是我們見面的時間。
4、This is why I am late.
這就是我遲到的原因。
5、My problem is which computer to choose.
我的問題是不知道選哪個電腦好。
但是，在下列情況下，表語從句做that 是可以省略的;
1、當主句中含動詞do的某種形式時，that可以省略。如：
What I want to do is (that) I can go up to him and thank him. 我想做的事是走到身邊去感謝他。
2、當句子的主語是：
advice, demand, decision, desire, idea, insistence, instruction, order, plan, proposal, recommendation, request, requirement, suggestion, wish等名詞時，表語從句須用虛擬語氣，即：should +do。如：
My advice is that you should go to apologize to him. 我的建議是你應該去向他道歉。
此外，除that 外，連線表語從句的連線詞還有： what, who, when, where, which, why, whether, how, whoever，whichever ，whatever等。還有如because, as if, as though等。
1、His suggestion is that we should stay calm.
他的建議是，我們應該保持冷靜。
2、The question is when he can arrive at the hotel.
問題是，他什麼時候可以到達酒店。