in which, for which, on which, at which, from which, to which, of which 用法
先看 1. 再看2. ，明白當中可以是從 preposition 調上來的。那就會知其所以然，明白詳細意思及用法。
in which 可翻譯成「在…裡面」
for which 可翻譯成「為了…目的」
on which 可翻譯成「在…上面」
at which 可翻譯成「在…某點上」
to which可翻譯成「要去的…. 位置」
The university in which he once studied is a famous one.
The situation in which we found ourselves was embarrassing.
Tomorrow I will bring the USB for which you asked.
I have a dresser on which contains varieties of cosmetics.
The castle at which I am pointing was built at mid-century.
The party at which he spoke was such a din.
The religious group from which I broke free was very perverse.
The town to which we were going was 100 kilometers away.
in/for/on/at/from/to/of which 的preposition 是從子句的最後調上來的，涉及到介詞Prep. ，我們在課程有詳解講解思意及用法。
The box in which the books are kept was bought.
= The box which the books are kept in was bought.
The town of which we were speaking is a famous one.
= The town which we were speaking of is a famous one.
The time at which we arrived was about noon.
= The time which we arrived at was about noon.
The destination to which we were heading is Hong Kong.
= The destination which we were heading to is Hong Kong.
She has married a celebrity （名人）‘of’ whom you must have heard.
= She had married a celebrity whom you must have heard ‘of’.
The castle which I am pointing ‘at’ was built at mid-century（中世紀）.
=The castle ‘at’ which I am pointing was built at mid-century.
其他preposition如under which, during which, about which, over which, etc. 都是同樣這樣用。 道理是一樣的。現在明白當中的意思了沒有？