1.多數(shù)情況下,關(guān)系代詞whom,which在從句中作介詞賓語時,可以跟介詞一起放在從句與主句之間（that,who不可以）,也可以把介詞放在從句中有關(guān)動詞的后面,使關(guān)系代詞緊跟它所修飾的先行詞.如：
He is a man of rich experience,from whom much canbe learned.
= He is a man of rich experience,whom much can be learned from.
他是個經(jīng)驗(yàn)豐富的人,從他那兒可以學(xué)到很多.
The school in which he once worked is a key school.
=The school (which that) he once worked in is a key school.
他曾經(jīng)工作過的學(xué)校是一所重點(diǎn)學(xué)校.
2.若介詞并不與從句中的動詞有關(guān)系,則要置前.如：
Fortunately we had a map,without which we would have got lost.
很幸運(yùn),我們帶了一張地圖,如沒有的話,我們就會迷路了.
3.如果介詞與從句中的動詞構(gòu)成固定搭配（短語動詞）,則不能置前.如：
The old man who nobody looked after felt very lonely.
沒人照顧的那位老人感到很孤獨(dú).