关系代词前介词的选择

在“介词+关系代词”引导的定语从句中，关系代词主要有which，whom，whose，它们既可以引导限制性定语从句，也可以引导非限制性定语从句。我们应如何选择关系代词前的介词呢？

一、介词与从句的先行词是习惯搭配

当先行词为时间名词或地点名词（该名词在主句中可充当主语、宾语、补足语、表语或者同位语等）时，我们应根据定语从句所修饰的名词前习惯搭配的介词来确定关系代词前的介词，此时的“介词+which”相当于when或where，在从句中作时间状语或地点状语。该定语从句既可以是限制性的，也可以是非限制性的。最常见的表示时间的介词有in，at，on，during，since，by，before，after，until等。如：

例1 Do you remember the day　 you joined our club？

A. on which B. of which

C. by which D. at which

解析：答案为A。先行词the day常与on搭配，构成介词短语on the day，在从句中作时间状语，所以用on which引导定语从句。

二、介词与从句的谓语动词是习惯搭配

当定语从句的谓语动词为含有介词的动词短语，且先行词在从句中作介词的宾语时，该介词可以移到关系代词之前，构成“介词+which/whom”引导的定语从句。在含有介词的短语动词中，由于动词和介词的关系比较紧密，一般不能将介词与动词拆开，也不能将介词提到关系代词之前。这类短语动词有listen to/look at/depend on/take care of/look into/break into/get rid of/look forward to等。如：

例2 Gun control is a subject　 Americans have argued for a long time.

A. of which

B. with which

C. about which

D. at which

解析：答案为C。从句的谓语动词argue与about构成习惯搭配argue about sth.，且关系词在从句中作介词about的宾语，介词前置，所以选C。

三、介词与从句中作表语的形容词是习惯搭配

当定语从句的谓语部分为“be+形容词+介词”，且先行词在从句中作该介词的宾语时，该介词可以提到关系代词之前，构成“介词+which/whom”。如：

例3 The woman　 Spielberg is married is an actress.

A. on whom B. to whom

C. by whom D. at whom

解析：答案为B。定语从句的谓语为固定搭配be married to，且先行词the woman在从句中作介词to的宾语，可将to提到关系代词whom之前，所以答案为B。

四、“数词/名词+of which/whom”引导的定语从句

当定语从句的引导词与先行词之间构成整体与部分关系时，我们常用“数词/名词+of　which/whom”引导，且“数词/名词+of　which/whom”常在从句中充当主语。如：

例4 The journey around the world took the old sailor nine months，　 the sailing time was 226 days.

A. on which B. of which

C. by which D. at which

解析：答案为B。先行词nine months与the sailing time之间构成整体与部分关系，即9个月中的航海时间，所以选B。

五、“the+名词+of which/whom”引导的定语从句

“the+名词+of which/whom”引导的定语从句，相当于“whose+名词”引导的定语从句，在定语从句中可作主语、宾语或表语。“of　which/whom”在从句中作定语，表示所属关系。如：

例5 Recently I bought an ancient Chinese vase，the price　 was very reasonable.

A. on which B. of which

C. by which D. at which

解析：答案为B。the price与先行词vase构成所属关系，the price of an ancient Chinese vase在从句中作主语，所以选B。

六、“介词+whose/which+名词”引导的定语从句

当先行词与从句中的某个名词构成所属关系，且该所属结构在从句中作介词的宾语时，即构成“介词＋whose＋名词”引导的定语从句。“介词+which+名词”结构可代替一些特殊形式中的that。选用哪个介词取决于先行词与定语从句中的谓语动词之间的关系，以及谓语动词常与哪个介词构成习惯搭配。如：

例6 Last month，part of Southeast Asia was struck by floods，　 effects people are still suffering.

A. from whose B. that C. those D. from what

解析：答案为A。 floods与effects之间是所属关系，且suffer from为固定搭配，floods’ effects在从句中作介词from的宾语，from可提前，所以选A。

七、“复杂介词短语+which”引导的定语从句

当先行词是复杂介词短语（on the top of/in the middle of/in front of/in spite of等）的宾语时，从句由“on the top of/in the middle of等+which”引导。复杂介词短语须保持其完整形式。如：

例7 Sound is a tool　 people communicate with each other．

A. at which B. for which

C. in view to which D. by means of which

解析：答案为D。先行词tool是by means of的宾语，by means of a tool 在定语从句中作方式状语，所以选D。

八、“介词 + where/when”引导的定语从句

当主句中作地点状语或时间状语的介词短语的宾语为先行词时，定语从句的引导词要使用“介词+where/when”，相当于“介词 + which place/time”。where指代that place或 there，when指代that time或then。此时，定语从句为非限制性定语从句。介词的选用，同样要符合定语从句的句意和搭配习惯。如：

例8 His head soon appeared out of the window，　 he saw nothing but trees.

A. from where B. from which

C. which D. at which

例9 The book was written in 1946，　 the education system has witnessed great changes.

A. when B. since which

C. since then D. since when

解析：答案分别为A、D。例8中依据句意“他的头很快从窗口探出来，从那里除了树木他什么也看不见”，要用from where，相当于from which place，指from out of the window。例9的原句可以理解为：The book was written in 1946，and since then the education system has witnessed great changes.　since when相当于and since 1946。（责任编校?筑彭益）