有一读者问： 有这样一句话：
(1)This is the book for which I have been looking.
为什么将 for 置于 which 之前？
旧时曾有不少人认为介词不应放在句子或从句之末。现今还有少数人抱有这种看法，尤其认为从句的末尾不应用介词。在当代英语中，介词不但可置于句末，如：
(2)They in the mountains have no school go to .
(3)It's not worth looking for .
(4)Where are you from ?
而且也可置于从句之末，如：
(5)It was what she had waited almost twenty years for .
(6)This is a bag which you can put the rubbish in ?
(7)The painting you're looking at has been sold.
由此可见，句（1）在当代英语中亦可改为：
(8)This is the book （which）I have been looking for .
但这并不是说，在当代英语中，介词不可置于关系代词 which 之前。上述句（1）并不显得古旧，只是比较正式罢了。其实，如果动词与介词没有固定的关系，即使在当代英语中，介词也是常置于 which 之前的，实例如：
(9)There is always a limit beyond which I cannot go. （go 与 beyond 虽常连用，但二者的关系不固定）
(10)They were trying to get the place as spotless as possible — even those areas through which it was most unlikely that any visitor would pass. （pass 与 through 也不是一固定的短语动词）
(11)He abandoned the business into which his family had put him. （put into 也不是一固定的短语动词）
