at which,in which,on which,for which,by which,from which的用法

主要看从句中的不及物动词,比如for which.
我们可以造个句子方便理解:This is the book for which he is looking.即等于This is the book which he is looking for.这主要是因为look for 这一短语.
which在从句中做宾语,如上句,还原就是 he is looking for which.
其中in which≈where, 这里就不赘述了.
希望这样能对您有所帮助~呵呵

at which 在******
in which 在******里面
on which 在******上面
for which 为了******
by which 用********
from which 从*******
以上是介宾短语 从当介词用