that不能引導定語從句的情況如下：
1. 在非限定性定語從句中不使用 that，而要用 which：I have read all the books, which were assigned by the professor last week.
2. 在由介詞引導的定語從句中不使用 that，而要用 which/what（指代物），或 whom（指代人）：
I have read all the books, three of which were assigned by the professor last week.
I could tell the difference, among whom I used to work with.
【拓展延伸】
定語從句中that的使用情況
1只用which,不用that的情況。
1)which可用在非限制性定語從句中。例如：
The project,which lasted four years,cost one billion dollars.這項工程歷時四年，耗資十億美元。
2)which可用前置介詞賓語。例如：
This is the house in which we lived three years ago.這是我們三年前住過的'那所房子。
2只用that，不用which的情況。
1)that相當於關係副詞when,where,why,in the way＝in which。例如：
I'll never forget the Monday that /when you first arrived.我將永遠不會忘記你初到的那個星期一！
Do you know anywhere that I can get fruit?
你知道我能在哪裏買到水果嗎？
I like the place for the very reason that/why you dislike it.我喜歡那地方的原因，恰恰是你不喜歡它的原因。
He doesn't see things the way that /in which we see them.他看問題跟我們不一樣。
2)that既可指物，也可指人。例如：
The people that worked on the project made a good effort.從事那項工程的人們做了很大努力。
3)當主句以here,there開頭時，常用that。例如：
Here is the place that you've been looking for.這就是你一直找的地方。
4)當先行詞是序數詞、形容詞最高級或先行詞被序數詞或形容詞最高級修飾時，常用that。例如：
The first(thing)that should bed one is to get the book.應該做的第一件事是弄到那本書。
This is the best place that I've ever visit-ed.這是我曾參觀過的最好的地方。
5)當先行詞是all,anything,nothing(something除外),none,little,much時，常用that。例如：
Is this all that's left?這就是剩下的所有東西嗎？
Have you got anything that belongs tome?你有沒有拿過屬於我的東西？
6)當先行詞被no,little,only,very,the last等修飾時，常用that。例如：
The only thing that could be done is to find
our way home.唯一能做的事情就是要找到回家的路。
7)當先行詞是兩個或兩個以上的詞分別表示人和物時用that。例如：
They talked about the teachers and the schools that they knew.他們談到了他們熟悉的老師和學校。
8)在以which，who開頭的句子中常用that。例如：
Which is the car that killed the man?撞死那個男子的小車是哪一輛？
9)time是先行詞時，前面如有序數詞或last修飾時，定語從句只能用that引導或省略。例如：
This is the last time(that)I shall give you a letter.
The first time(that)I saw him was last year.
