系副词即表时间when，地点where ，原因why, 等词，在句中的具体用法要看句子的意思了。 介词加
关系代词一般情况下就是介词加which的情况，即in which = where/when (大的时间年月季等或大的地点国家、城市等) at which=where/when(小的时间点 某一时刻 或小的地点 在学校、家等) for which=why 因此，在
定语从句中，有介词时，必选which，其意与所对应的
关系副词是一样的。
还要根据句子的结构搭配哦
选用介词的依据：
(1) for which=Why
Yesterday we visited the West Lake for which Hangzhou is famous.
(2) with whom和某人
The
old woman with whom you talked just now is a famous artist.
(3) through which穿过某处
The naughty boy made a hole in the wall through which he could see what is happening outside.
(4) 表示“所有”关系或“整体中的一部分”时，通常用介词of。例如：
I have about 20 books, half of which were written by Bing Xin, the famous writer.
(二)在定语从句中，含介词的短语动词不可拆开使用(短语拆开后含义发生变化)，如look after, look for等。例如：
The babies whom the nurses are looking after are very healthy.(正)
The babies after whom the nurses are looking are very healthy.(误)
【三】“of which / whom”有时可以用“whose＋名词”结构来改写。例如：
The building whose roof was damaged in the earthquake has been repaired.
＝The building of which the roof was damaged in the earthquake has been repaired。
好了，报告完毕。。。。。