Because of my poor memory, all ___ you told me has been forgotten.

a. that b. which c. what d. those
选A， 怎么分析呢？

这是that和which在定语从句中用法的问题
当先行词是all时，用that
下面的这个是你必须了解的

注意1 that \which在代物时常常可以通用,但有时只宜于用which ,不用that

(1) 关系代词前有介词时.

This is the hotel in which you will stay.

(2) 如有两个定语从句,其中一句的关系代词是that,另一句宜于用which.

Let me show you the novel that I borrowed from the liberary which was newly open (新开放) to us.

注意2that \which在代物时常常可以通用,但有时只宜于用that ,不用which.

(1) 先行词是形容词最高级或者它的前面有形容词最高级时

This is the best that has been used against air pollution(反对空气污染) in cities.

English is the most difficult subject that you will learn during these years.

(2) 先行词是序数词,或它的前面有一个序数词时

He is the last person that I want to see.

(3) 主句中已有疑问词时

Which is the bike that you lost?

(4) 先行词既有人又有物时

The bike and its rider that had run over (撞倒了)an old man were taken to the police station.

(5) 先行词是all,much,little,something,everything,anything,nothing,none,the one等代词时

You should hand in all that you have.

We haven’t got much that we can offer you.

I mean the one that you talked about just now.

(6) 先行词前面有only,any,few,little,no,all,one of,the same,the very等词修饰时

The only thing that we can do is to give you some money.

Li Ming is the only one that got full marks (满分)in our class.

Li Ming is one of the students that want to be teachers in our class.

(7) 有两个定语从句,其中一个关系代词已用which,另外一个宜用that

Edison built up a factory(办了一个工厂) which produced things that had never been seen before.

答案a 不定代词all后面应由that引导定语从句。

all引导从句时，后面只能加that!

all that 到那种程度[地步] 其他选项没有这些结构

all that=what