英语介词和关系代词
北师大家教网：1）介词后面的关系代词不能省略。
2）that前不能有介词。
3） 某些在从句中充当时间，地点或原因状语的"介词+关系词"结构可以同关系副词when ,where和why 互换。
This is the house in which I lived two years ago.
This is the house where I lived two years ago.
介词+关系代词引导的定语从句关系代词在定语从句中做介词宾语时
从句常由介词+关系代词引导
当介词放在关系代词前面时，关系代词只能用which/whom即“介词+which/whom"且不能省略。但当介词位于末尾时可用that/which/who/whom.作介词的宾语，且可以省略。例如：
(1) The school (that/which) he once studied in is very famous."that/which"可以省略
= The school in which he once studied is very famous."which”不可省略
(2) Tomorrow I will bring here a magazine (that/which) you asked for.
= Tomorrow I will bring here a magazine for which you asked.
注意：
1. 含有介词的动词短语一般不拆开使用，如：look for, look after, take care of等
T This is the watch which/that I am looking for. (T＝正确)
F This is the watch for which I am looking. (F＝错误)
2. 若介词放在关系代词前，关系代词指人时用whom，不可用who或者that；指物时用which，不能用that；关系代词是所有格时用whose
(1) The man with whom you talked is my friend. (T)
The man with that you talked is my friend. (F)
(2) The plane in which we flew to Canada is very comfortable. (T)
The plane in that we flew in to Canada is very comfortable. (F)
3. “介词+关系代词”前可有some, any, none, both, all, neither, most, each, few等代词、数词或者名词。
(1) He loved his parents deeply, both of whom are very kind to him.
(2) In the basket there are quite many apples, some of which have gone bad.
关系代词
关系代词（一般情况下）that 可用在从句做主语，谓动词的宾语，但是不能做介词的宾语。
which指物，在从句中作主语，谓语或宾语；
who在从句中作主语；
whom在从句中作宾语；
where在从句中修饰表地点的名词，做地点状语；
when在从句中通常修饰表时间的名词，做时间状语；
why在从句中做原因状语，先行词通常是"reason"
有时why也可用for+which代替。
例：A doctor is a person ‖who looks after people's health.
主语 谓语 先行词 定语从句修饰先行词
判断介词和关系代词
方法一： 用关系代词，还是关系副词完全取决于从句中的谓语动词。不及物动词后面无宾语，就必须要求用关系副词或者是介词加关系代词；而及物动词后接宾语，则要求用关系代词。例如：
This is the mountain village where I stayed last year.
I'll never forget the days when I worked together with you.
判断改错（注：先显示题，再显示答案，横线；用不同的颜色表示出。）
（错） This is the mountain village where I visited last year.
（错） I will never forget the days when I spent in the countryside.
（对） This is the mountain village (which) I visited last year.
（对） I'll never forget the days (which) I spent in the countryside.
习惯上总把表地点或时间的名词与关系副词 where, when联系在一起。此两题错在关系词的误用上。
方法二： 准确判断先行词在定语从句中的成分(主、谓、宾、定、状)，也能正确选择出关系代词/关系副词。
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