1、定语从句中关系词必须用 that 的情况： 1. 被修饰的先行词是不定代词 all，much，something，everything，nothing，none，the one 等时， （注意：表示人的不定代词即可用 that 也可用 who/whom） 如：Anyone who/that doesnt like this film must tell me. Do you have something that is very difficult to understand? All（that）I can do is to give him some hope. 2. 被修饰的先行词还有一些
2、特定意义的修饰词，如：the only、the very、just the、the right、any 、every、no、all、 much、many、little、few 等， 如：The only thing（that）we know is that the universe is very big. Any bus that can go there is OK. This is just the/the very/the right book I am looking for. There are few cars that are driving slowly. Every car
3、 that has a high price is worth what it costs. 3句子中出现过 which 或 who 之类的词，为了避免重复，要用 that， 如：Who is the man that is speaking? The factory which produces shoes that are very good has gone bankru4关系代词在从句中作表语时，多用 that。如： She is not the girl that she was three years ago 5先行词被形容词最高级、only 等修饰时，应用 that。如： Tan
4、g Guoqiang has become one of the best actors that appear on Chinese screens 6. 先行词既有人又有物或 time， 如：Can you tell me the people and events（that ）you saw in Britain? The man and his dog that looked odd came to me quietly. Each time that he came here, he would like to talk with her. 5关系代词与 the same（指同一人）
5、连用时，只能用 that。如： This is the same person that I met yesterday 7一个句子中有两个定语从句时，如第一个从句中已用 who，第二个从句中宜用 that。如： The man who is at table is his brother that has been serving in the army 8当先行词是 to be 的表语，或关系代词本身是从句的表语时，关系代词应用 that。如： 1）Its a song that is very popular 2）My hometown is no longer the place th
6、at it used to be 5当主句以 There be 开头时，关系代词应用 that。如： There is a seat in the corner that is still free 9当一个句子中含有两个定语从句时，如前一个已用关系代词 which，后一个关系代词宜用 that。如： Ill borrow a book which tells about the heroic deeds that the PLA did in the battles against the invaders 但两个定语从句的结构如果平行，一个定语从句中用关系代词 that，另一个定语从句也应重复 that。如： He told me to read a book that is very short，and that is very interesting 10与 the same（指同一物）连用，构成 the same that 结构时，关系代词只能用 that。如： This is the same museum that you once visited 注意：the same that 结构中的 that 不能用 as 代替，因为 the same as 与 the same that 的含义不同。
