3. The beginning of agriculture was a big step in human progress with which nothing could compare until our information age.

2.Do you know the person with whom I shook hands？= Do you know the person (whom/who/that) I shook hands with?

1. This is the book for which you asked.

=This is the book (that/which) you asked for.

5. A child whose parents are dead is called an orphan.(指人)

I'd like a room whose window faces south. (指物)=I'd like a room of which the window faces south. =I'd like a room the window of which faces south.

There is a teapot shaped like a Chinese duck, out of whose mouth tea is supposed to come

关系代词作介词宾语:

关系代词在定语从句中用作介词宾语时, 介词可放于从句之首, 也可放于从句之末. 但以放于句首较为正式.(介词前置，必须注意不影响动词词组的含义。关系代词who 和 that 用作介词宾语时, 介词必须放在句末.) 如:

4.He's a man from whom we should learn. = He's a man (whom/who/that) we should learn from.

比较：He is the student whom you think to be worthy of your praise.

He is the student who you think is worth praising.

3.Chaplin, for whom life had once been very hard, was a success as an actor.　 (宾语)

2.All who heard the story were amazed. (代词如he, they, any, those, all, one等后多用who.)

who: 主格, 在从句中作主语，在口语或非正式用法中作宾语; 只可指人

whom: 宾格，在从句中作宾语; 只可指人

whose: 属格，在从句中作定语，可指人也可指物。

1.I like the students who/that work hard. (主语)

6. He may be late, in which case we ought to wait for him.

5. Tom spent four years in college, during which time he learned French.(定语)