21．Here is a picture of Lei Feng ____ ____ we learned a lot.

20．The book ____ ____ they are talking on and on is very interesting.

19．The world ____ ____ we live is made of matter, which has three states.

18．To tell you the truth, the man ____ ____ you are waiting won't come tomorrow.

17．The fellow ________ I spoke made no answer. Perhaps he's deaf.

16．I'll never forget the soldier ____ ____ I was saved from the river on a freezing morning.

15． There's no doubt that this is not the way ________ I came last time.

14． The farm ____ ____ my father once worked has taken on a new look for the time being.

13． The desk ____ ____ Tom is leaning is Jack's. It's covered with dictionaries.

12． Ours is beautiful school with a long history, ________ we are proud.