一、基本构成及用法
[合作探究] 画出下列句子中的“介词＋which/whom”结构。
①The ladder on__which I was standing began to slip.
②They tried to think of a plan by__which they could complete their task ahead of time.
③I met a man with__whom I used to work.
④We'll go to see the famous singer about__whom we have talked.
[自主发现]
(1)关系代词在定语从句中作介词的宾语时，从句常由“介词＋which/whom”引导。
(2)若介词放在关系代词前，关系代词指物时只能用which；关系代词指人时只能用whom。
