几种特殊的定语从句
■since / until / by when引导的定语从句
定语从句中有一类是since / until / by when引导的定语从句, 这类比较特殊的定语从句，一般都可整合为and连接的并列句。and since / until / by then= since / until / by when
借助并列句分析解此类定语从句，就会简单易懂易记。
【典型例题1】
The book was written in 1946, _______ the education system has witnessed great changes.
A. when B. during which
C. since then D. since when
【解析】句意：该书写于1946年，从那以后教育制度已经历了 巨大变化。因从句中“has witnessed”是完成时，而只有含 since引导的时间状语句子才用完成时，故此句可改写：
The book was written in 1946, and since then the education system has witnessed great changes.
【典型例题2】
The baby is due in May, _______ the new house should be finished.
A. by then B. which
C. by when D. since when
【解析】句意：“那个婴儿五月将出生，到那时他 / 她家的新房应该能装修完毕了。”故此句可改写：
The baby is due in May, and by then the new house should be finished.
【典型例题3】
I am going back to my hometown this summer, ________I will have enough time to buy a car.
A. by then B. which
C. by when D. since when
【解析】句意：今年夏天我打算回家乡，到那时我就会有足够的时间买辆车。从句的时态是将来时，所以排除D，从句中的成分是完整的，排除Ｂ，by then不能引导从句，by when在句意和时态上都吻合题意，相当于and by then,故故此句可改写：
I am going back to my hometown this summer, and by then I will have enough time to buy a car.
【典型例题4】
Tom has been living a comfortable life, _______his parents run away due to heavy debts.
A. until then B. until when
C. since then D. since when
【解析】句意：Tom在父母亲的照顾下，过着富裕的生活，直到他父母由于沉重的债务跑掉了。until then 和since then 不能引导从句，since when时态需要用完成时，正确答案是B。
本句可以改写为：
Tom has been living a comfortable life, and until then his parents run away due to heavy debts.
■which + n. 引导的定语从句
which可以加概括意义的名词，引导定语从句。
and during / by that time=during / by which time 在那段时间
and in that case = in which case 在那种情况下
and at that point = at which point 在那时
and that language = which language 那种语言
【典型例题1】
He can speak German, ________language I can only follow with difficulty.
A. that B. whose
C. which D. what
【解析】句意：他会说德语，那种语言我要很费力地才能听懂。A,D不能引导非限制性定语从句，whose和language的关系不是所属关系，所以答案是which 。此句可改写：
He can speak German, and I can only follow that language with difficulty.
【典型例题2】
She may be late, ________we ought to wait for her.
A. in which case B. in that case
C. where D. from where
【解析】句意：她可能迟到，那种情况我们该等她。C,D与题意不吻合，in that case不能引导从句，in which case 能引导从句，而且和词组吻合。本句可改写成：
He may be late and in that case we ought to wait for him
【句子转换】
1. 他被任命为主席，在那个位置上他度过了余生。
He was appointed chairman, in which post he spent the rest of his life.
= He was appointed chairman and in that post he spent the rest of his life.
2. 他发了脾气，在那个时刻我决定回家。
He lost his temper, at which point I decided to go home.
= He lost his temper and at that point I decided to go home.
3. 在家里，他好像十点半之后才有空，到那时孩子们已上床睡觉了。
At home, he never seems to have time until after 10:30 pm, by which time his children have gone to bed.
= At home, he never seems to have time until after 10:30 pm, and by that time his children have gone to bed.
4. 我们做了三年隔壁邻居，在此期间我们只见过两次面。
We were next-door neighbors for three years, during which time we met only twice.
= We were next-door neighbors for three years, and during this / that time we met only twice.
5. 被告知我的工作不能令人满意，闻讯后我便递交了辞呈。
I was told my work was unsatisfactory, at which point I submitted my resignation.
= I was told my work was unsatisfactory, and at this / that point I submitted my resignation.
6. 他在学习经济学，这门知识在当今非常重要。
He is studying economics, which knowledge is pretty important today.
= He is studying economics, and this knowledge is pretty important today.
■after / before which 引导的定语从句
and after / before that = after / before which
【典型例题1】
He was educated at a local grammar school, _______ he went on to Cambridge.
A. from which B. after that
C. after which D. from this
【解析】句意：他在当地一所文法学校上学，之后他便去了剑桥。after that意为“然后，之后”，但不能引导一个定语从句，因此B项也被排除；after which相当于and after that，故此句可改写为：
He was educated at a local grammar school, and after that he went on to Cambridge.
【典型例题2】
He left his hometown 20 years ago, _______nothing was heard about him.
A. since when B. after that
C. after which D. from this
【解析】句意：20年前他离开家乡，从那以后再没有他的消息。Since when与与过去时态不吻合，需要用完成时；B,D不能接定语从句，所以C正确。本句改写成：
He left his hometown 20 years ago and after that nothing was heard about him.
句子转换
我在东关中学工作了九年，之前我在光明中学工作。
I worked in Dongguan Senior Middle School for 9 years, before which I worked in Gunagming Senior Middle School.
= I worked in Dongguan Senior Middle School for 9 years, and before that I worked in Gunagming Senior Middle School.
【小结点拨】
根据上述学习内容，做出如下总结：
1.带有this, that的短语，引导定语从句时，要将this, that变为 which。
2.带有then, now的短语，引导定语从句时，要将then, now变为when。
巩固练习：
1.He believes in public ownership, ______ idea I quite opposed to.
A. this B. that C. which D. what
2.The baby is due in May, _______ the new house should be finished.
A. by then B. by which C. by when D. since when
3.Mark was a student at this university from 1999 to 2003, _______ he studied very hard and was made Chairman of the Students’ Union.
A. during which time B. for which time
C. during whose time D. by that time
4. The new China was founded in 1949, _______ great changes have taken place.
A. when B. during which C. since then D. since when