21.　 ______is mentioned above, the number of the students in senior high schools in increasing.

A. Which　　　　 B. As　　　　　 C. That　　　　　 D. It

20.　 We had to delay the party till next week, _____ we would have something important to do.

A. when　　　　　 B. which　　　　　 C. while　　　　　 D. before

19.　 I hope you will find this valley a beautiful place ______ you may spend your weekend.

A. which　　　 B. that　　　 D. when　 　　D. where

18.　 Have you ever been to Shanghai, ______ I left then years ago?

A. which　　 B. where　　 C. that　　 D. when

17.　 We saw the hill, and ________ there used to be a factory.

A. in front of which　 B. on the top of which　 C. at the foot of it　 D. from it

16.　 Do you know the professor in ______ hometown we stayed?

A. which　　　 B. his　　　 C. whose　　　 D. whom

15.　 It’s the playground ______ I picked up this jacket.

A. from which　　 B. that　　 C. from where　　 D. where

14. The Great Wall is the last place ______ Mr. Smith is going to visit before he leaves Beijing.

　 A. where　　　　　 B. which　　　　　 C. /　　　　　 D. what

13.　 He lent me $1,500 ______ I bought a diamond necklace for her.

A. by which　　 B. in which　　 C. on which　　 D. with which

12.　 Mount Blanc, ______we visited last summer, is the highest mountain in Europe.

A. where　　　　 B. that　　　　 C. which　　　　 D. what