1．关系代词前介词选择的原则
(1)根据定语从句中的谓语动词或形容词和介词的搭配关系选择。
There comes Tom, for whom I have been waiting an hour or so.
汤姆来了，我等了他大约一个小时了。
(2)根据定语从句中介词与先行词的搭配关系选择。
The old woman with whom you talked just now is a famous artist.
刚才和你们说话的老太太是一个著名的艺术家。
(3)根据句子的意思选择。
Thank you for your help, without which we couldn't have finished the task on time.
谢谢你的帮助，没有你的帮助，我们就不能按时完成任务。
