三个关系代词“who/that/which/ , 完全可以指代“单数名词/复数名词”或者“单数代词/复数代词”引导定语从句，这是不用质疑的。这种语言现象十分常见在英语课文，英语小说，英语文章，英语杂志以及所有的英语语法书中都随处可见，不需要权威语词典，正规词典或语法著作提供。网友可以放心使用。

【1】单数名词+who/which/that+从句

The man who is sitting next to Tom comes from the UK.

This is the house that Tom bought two years ago.

The car which Mike’s father bought five years ago is still new.

【2】复数名词+who/which/that+从句

The boys who came to Tom’s birthday party last night are his best friends.

The pens which were bought by his father last year write so smoothly.

Those trees that were planted five years ago are growing well

【3】单数代词+who/which/that+从句

He who laughs last laughs best.

He who makes no mistakes makes nothing.

What’s that which is under the desk?

【4】复数代词+who/which/that+从句

Those that are interested in the job should apply for it.

Those who break the law will be punished.

Those who want to visit the science museum may sign their names on the paper.

Those +that引导定语从句 是不用质疑的。