求完形填空答案I was a mathematics graduate student at the Universit

求完形填空答案
I was a mathematics graduate student at the University of California,Berkeley.Coming late to class as usual,I quickly__16 the two math problems from the blackboard,thinking they were the homework.When I sat down to 17 on them that evening,I found them to be the most 18 problems my professor had ever given us.Night after night l worked,trying first to solve one then the other with no 19 .But I kept at it.
　　Several days later,I made a breakthrough(突破)and 20 both problems.I took the homework to class the next day.The professor told me to 21 it on his desk.It was piled so high with papers that I was afraid that my homework would get lost in the mess.22 ,I dropped it off and went on my way.
　　Six weeks later,on a Sunday morning,1 was awakened by some loud 23 on the door.1 was a bit shocked to see it was my professor.He 24 that the two problems on the blackboard were not homework,they were two famous outstanding problems that leading mathematicians so far had not been able to solve.He could 25 believe that in only a few days I had worked them both out.
　　If someone had told me that they were two famous unsolved problems,I probably wouldn't have even tried to solve them.It goes to show the power of positive thinking.
　　16.A.asked B.understood C.noticed D.copied
　　17.A.carry B.get C.work D.decide
　　18.A.interesting B.boring C.difficult D.meaningful
　　19.A.problem B.way C.success D.failure
　　20.A.did B.found C.solved D.discovered
　　21.A.leave B.give C.keep D.stick
　　22.A.Hurriedly B.Excitedly C.Happily D.Unwillingly
　　23.A.knocks B.noises C.sounds D.shouts
　　24.A.answered B.announced C.explained D.argued
　　25.A.surely B.hardly C.honestly D.firmly

16.D
17.C
18.C
19.C
20.C
21.A
22.A
23.A
24.C
25.B