介词加关系代词的用法？

situation,occasion case 等做先行词时 只需填关系副词而已 凡是关系副词都可以转换成介词+which 此时从句少的肯定是状语 有时候介词+关系代词不能用关系副词来表示 就是从句少的不是状语 那么介词 有三种来源 1 看先行词 如 the train 你只能用on which 不能用by which 2 看从句的谓语动词的固定搭配 如 drop in on whom drop in at which 3看整个句子 比如用through which without thich 等 我没有例举完整的句子 你能明白吗？在做题目时 应该遇到类似的题型。

你的问题是高中生经常问的问题，弄清楚很有要。其实这是定语从句中介词前置造成的。比如This is the hotel at which I stayed during the vacation.这句中的which 指的是hotel.把上句分解成两句话就是：This is the hotel. I stayed at the hotel.更多例句：
Fortunately we had a map,without which we would have got lost.
Police are talking about ways in which computers can help fight against crime.
The old man has three daughters, one of whom is a doctor.