英语问题

Question

介词+关系代词，可以用相应的关系副词when或where替换，怎样理解？
eg：this is the picture about which they are talking。这句可以等于this is the picture that they are talking about吗？

Answer 1

不是所有的介词+关系代词which都可以用when或where来代替的。
当介词+which表示：在这个时间、在这个地方时，可以用when或where替换。
象你举例的这句中about which就不能用where更不能用when来替换。
可你又问到另一个问题上去了，那就是介词放在关系代词前还是留在原处的问题。
如果不是和动词结合的很紧的介词如look for, look after，象talk about这样的介词，放前放后都可以的。

Answer 2

定语从句中“介词+关系代词”，的用法：
指人：介词+whom
指物：介词+which
介词的确定是根据：
1.与先行词的搭配，确定介词。
That was the year in which I visited the Summer Palace. 可转换成That was the year when I visited the Summer Palace
2.与谓语动词的搭配，确定介词。
This is the place in which I live.可转换为This is the place where I live.
在定语从句中， 当介词+which(which指代表地点的名词）时，可用where来替换；若为介词+which(which指代表地点的名词时），可用when来换 。
This is the picture about which they are talking. 这句可以等于This is the picture that they are talking about.
又如：This is the place in which I live. 可转换成This is the place that I live in.
当然有部分短语不能拆分，如楼主所说的look for。

Answer 3

定语从句中：
关系副词 指代 在从句中的作用
when(=at/in/on/during which) 时间 时间状语
where(=in/at which) 地点 地点状语
why（=for which） 原因 原因状语
在介词后面，指事物用which，指人用whom
This is the picture about which they are talking这句的表达好像不大对，第二局就是对的