【问】 ×My sister，that is a nurse，came home for a few days.

×She was very fond of speaking French，that indeed she spoke well.

有人说句中的that是错误的。难道疑问代词that不能用于定语从句来代替who和which吗?

【答】 首先应当分清定语从句是限制性定语从句，还是非限制性定语从句。在限制性定语从句里可以使用关系代词that，这是毫无疑义的。

1. They live in a house that was built in 1600. (Eckersley)

他们住在一所建于1600年的房子里。

2. She is the girl that you saw in school. (Thurndike)

她就是你在学校里见到的那个女孩。

但是，在非限制性定语从句中一般不使用关系代词that，而使用who (whom)或which：

1. I spoke to Dr Spolsky，who was unwilling to give further details. (CGEL)

2. I spoke to Dr Spolsky，whom I met after the inquest. (CGEL)

3. She heard a terrible noise，which brought her heart into her mouth. (全国高考英语试题，1991)

[参见that(pron.)⁶]