结构的由来

在定语从句概念中推导定语从句的由来中阐述了关系代词和先行词。在这里，同样一步步推导"介词+which/whom"结构的由来。

介词+which

下面有两个独立的句子，逻辑上属于一个句子，都有相同的名词：

【例句】My elder sister works in the famous university. She graduated from the famous university last year.
【翻译】我姐姐在那所著名的大学工作。她去年从那所名牌大学毕业。

第二个句子中的"the famous university"作介词 from 的宾语。把这两个句子合并成一个定语从句：

My elder sister works in the famous university, from which she graduated last year.

关系代词 which 指代"the famous university"。通过例句得知，which 作为 from 的宾语，因此，形成“from+which”的结构。

介词+whom

【例句】This is the student. I bought the book for him.
【翻译】这就是那个学生。我给他买了这本书。

him 与 student 说的都是那个学生。him 是人称代词的宾格形式，与 whom 等同。用 whom 作介词 for 的宾语。改造这个例句成一个定语从句：

This is the student for whom I bought the book.
【翻译】这就是我给他买书的那个学生。

小试牛刀

Last week we bought a beautiful house, (____) the walls were painted light blue.

A. which
B. of which
C. its
D. whose

【解析】B。该句子是一个定语从句，关系代词不可能是 its，所以排除选项 C。先行词 house 是一个物，所以排除选项 D。从句 the walls 属于 house，在逻辑上是 the walls of house，walls 是 house 的所有格；很明显，of which 才符合这一逻辑。