三、介词的选用

介词+关系代词引导定语从句时，介词往往受上下文的约束，究竟使用哪个介词时得从下面几方面来进行考虑。

(1) 从先行词跟介词的搭配习惯出发。如：

In front of my house, there is a tree, in which some birds are singing. 我的房子前有一棵树，鸟儿正在树上唱歌。(在树上一般用介词in)

(2) 从定语从句中的动词、形容词对介词的习惯要求出发。如：(from www.hxen.com)

The computer for which I paid 5,000yuan is made in Shenzhen. 我花了五千元所买的这台电脑使深圳造的。( pay 与for搭配)

(3) 从先行词、定语从句中的动词或形容词两方面同时考虑出发。如：

Do you know the girl with whom the man talked just now? 你认识跟那个男谈话的女孩吗？(talk 究竟接to, with还是接about, 这该由动词及现行词一起决定)

(4) 复合介词+关系代词。如：

Go down this road, at the end of which you can see a high building and it is our office building. 沿着条路走，在路的尽头你会看到一座高大的建筑，那就是我们的办公大楼。

(5) 名词+介词+ 关系代词。如：

He has three children, one of whose children is studying abroad now. 他又三个小孩，其中一个在国外读书。

注意：当定语从句的动词与介词是不可分割的固定搭配时，介词不能放到关系代词之前。如：

She has a little daughter, who is looked after by her grandma. 就不能写成：She has a little daughter, after whom is looked by her grandma. 因为，look after 是不可分开的固定短语。