15. If metal is heated and then cooled very quickly, 　　　　, by dipping in cold water, it will be very hard but will break easily.

A. what’s more　　　　 B. in general　　　　　　 C. for example　　　 D. on the other hand

14. Even though he has failed many times, he holds a belief _____ he will succeed one day if he works hard.

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

13. At the meeting, they sat very_____ and had a _____ talk, but I didn’t know what they were talking about.　　　

A. close; close　　 B. closely; close　　 C. close; closely　　 D. closely; closely

12. -What do you think of the exhibition?

　 -I suggest ______ another visit to it.

　　 A. to pay　　　　 B. paid　　　　　　 C. paying　　　　 D. having paid

11. _________her absence, the students behaved so well that she was proud _______it.

　 A. in; with　　　　　 B. On; in　 　　　　C. At; of　　　　　　 D. During; of