Question

定语从句引导词问题修饰人时，that和who的区别

Answer 1

先行词指人时，关系代词既可用who，亦可用that。但关系代词在从句之中用作主语时，多用主格who。如：
Persons who are quarrelsome are despised. 好争吵者遭轻视。(除外persons，还有people，those，等皆多用who)
All who heard the story were amazed. 听到这个故事的人都感到吃惊。(代词如he，they，any，all，one等之后多用who)
I will pardon him who is honest. 我愿意宽恕他，他是诚实的。(描述性定语从句用who)
I think it is you who should prove to me. 我认为是你应该向我提出证据。(在强调结构中多用who，who在此可省去)
Who is not for us is against us. 谁不赞成我们就是反对我们。(缩合连接代词who为可代之以that)
在下列一些情况中则多用that。如：
)He was the man that the bottle fell on. 他就是瓶子落在其身上的那个人。(此处常用that作宾语指人，亦可用whom)
He is a man that is never at a loss. 他是一个从未一筹莫展的人。(that常用于泛指人)
He was watching the children and parcels that filled the car. 我望着塞满车的孩子和包裹。(兼指人与物时须用that)
Who that you have ever seen can beat him in chess? 你曾见过谁能在棋艺上打败他?(避免与先行词who重复时应用that)
That’s the same man that asked for help the day before yesterday. 这个与前天求援的是同一个人。(先行词前有指示代词same时应用that)
He is not that man that he was. 他已不是过去的他了。(that常用作表语)
I knew her father for the simplest, hardest working man that ever drew the breath of life. 我早知她的父亲是一个世上最简朴最努力工作的人。(先行词前有形容词最高级、序数词或only等词时应用that)

希望我能帮助你解疑释惑。

Answer 2

没有很大区别，但是在一定的特殊情况下，只能用that 或只能用who
只能用that;
1.当先行词为anything，everything，nothing等不定代词时，只能使用“that”。
例：Is there anything that I can do for you? 我能给你做点什么吗?
2.当先行词为all，any，much，many词时，只能使用“that”。 例：Tom told her mother all that had happened. 汤姆把事情的全部情况告诉了他的妈妈。
3.当先行词是形容词最高级或被形容词最高级修饰时，只能使用“that”。
例：This is the most wonderful time that I have ever had. 这是我度过的最美好的时光。
4.当先行词是序数词修饰时，只能使用“that”。 例：He was the first person that passed the exam. 他是第一个通过考试的人。
5.先行词被the only，the very，the same，the last修饰时，只能使用“that”。
例：This will be the last chance that he can get. 这将会是他得到的唯一机会。
He is the only person that can help you out. 他是唯一能帮你的人。
6.先行词里同时含有人或物时，只能使用“that”。
例：They talked of things and persons that they remembered in the school.
他们谈论他们记得的有关学校的事和人。
7.当主句是以who，which开头的特殊疑问句或先行词是who时，只能使用“that”。
例：Which is the book that he bought from the library yesterday? 哪本是你们昨天从图书馆借的书？