賓語從句或表語從句中that有時(shí)可以省略,但在以下情況時(shí),that不宜省略.
一、當(dāng)動詞后帶有兩個(gè)并列的賓語從句時(shí),引入第二個(gè)從句的連詞that不可省略.例如：
The teacher told the students (that) they should hand in their homework the next day and that the homework must be signed names by their parents.老師告訴學(xué)生他們要在第二天交上作業(yè),并且作業(yè)必須由家長簽名.
二、當(dāng)that前面有插入語時(shí),that不宜省略.例如：
Little Alice didn't know,I'm sure,that her sister was going to America.我確信,小艾麗斯不知道她的姐姐很快就要去美國了.
三、省略答語中,that賓語從句單獨(dú)出現(xiàn)時(shí),that不可省略.例如：
—What did he say?他說了什么
—That he would visit the Great Wall.(他說)他將會參觀長城.
四、當(dāng)主句的狀語部分位于that 賓語從句之前時(shí),that不宜省略.例如：
Jane realized at once that she must do with it herself.珍立刻意識到她必須親自處理那件事.(如省略that,at once也可能修飾從句,是表示“立刻意識到……”,還是表示“立刻去處理……”,較為含糊)
五、 當(dāng)that 賓語從句中的狀語部分位于從句的前部時(shí),that不宜省略.例如：
Tom promised that if he could earn as much as 500 dollars in this month,he would buy a computer for his brother.湯姆許下諾言,如果他在這個(gè)月里能夠賺到500美元,他就給他的弟弟買臺電腦.
六、當(dāng)that 賓語從句是雙賓語中的直接賓語時(shí),that一般不宜省略.例如：
I will never tell anyone that you have ever been there.我絕對不會告訴別人你曾經(jīng)去過那兒.
七、當(dāng)為了強(qiáng)調(diào)而把that引導(dǎo)的主語從句位于句首時(shí),that不可省略.例如：
That they would take the risk was very clear.他們將要冒這個(gè)險(xiǎn)是很清楚的了.
八、當(dāng)主句中的謂語動詞是固定詞組時(shí),其賓語that 從句中的 that 不宜省略.例如：
Mary has made up her mind that she will study hard for the scholarship,so she can have the chance to go abroad for further study.瑪麗下定決心努力學(xué)習(xí)以獲得獎學(xué)金資格,這樣她就有機(jī)會出國深造了.
九、當(dāng)that 賓語從句前有 it作其形式賓語時(shí),that不可省略.例如：
We think it important that college students should master at least one foreign language.我們認(rèn)為大學(xué)生至少掌握一門外語是很重要的.
十、當(dāng)引導(dǎo)同位語從句時(shí),that一般不可省略,尤其當(dāng)that與先行詞處于分割情況時(shí).例如：
He heard the news that his team had won.他聽到了他的隊(duì)獲勝的消息.
The police report that the drugs had been found appeared in the press yesterday.毒品已經(jīng)被發(fā)現(xiàn)這一警察報(bào)告昨天見報(bào)了.
There is a feeling in me that they are cheating me.我有一種感覺他們在騙我.
十一、當(dāng)that 賓語從句的主語是非謂語動詞或是主語從句時(shí),that不可省略.例如：
The doctor said that taking exercise was the best way of losing weight.醫(yī)生說運(yùn)動是最好的減肥方式.
The old lady then explained that what she was looking for was a pair of gloves for a girl.老太太然后說她尋找的是一雙女孩子戴的手套.
注意：當(dāng)名詞性從句已有疑問詞引導(dǎo)時(shí),不可再加that.例如：
I don't understand that what you said just now.(×)
I don't understand what you said just now.(√)