55. Sales of CDs have greatly increased since the early 1990s, when people _____ to enjoy the advantages of this new technology.

　A. begin　　　　 B. began　　　　　 C. have begun　　 D. had begun

54. Because the shop ____, all the T-shirts are sold at half price.

　A. has closed down　 B. closed down　 C. is closing down　　 D. had closed down

53. The discussion _____ alive when an interesting topic was brought in.

A. was coming　　　 B. had come　　　 C. has come　　　　 D. came

52. ----You were out when I dropped in at your house.

　----Oh, I ____ for a friend from English at the airport.

　A. was waiting　　 B. had waited　　 C. am waiting　　 D. have waited

51. She ___ her hairstyle in her hometown before she came to Chongqing for a better job.

　 A. would change　 B. has changed　　 C. changed　 D. was changing

50. The crazy fans ___ patiently for two hours, and they would wait till the movie star arrived.

A. were waiting　　 B. had been waiting　　 C. had waited　　 D. would wait

49. The first use of atomic weapons was in 1945, and their power _____ increased enormously ever since.

A. is　　　　 B. was　　　 C. has been　　 D. had been

48. ----What were you doing when Tony phoned you?

　----I had just finished my work and ___ to take a shower.

A. had started　　　 B. started　　 C. have started　　 D. was starting

47. Now that she is out of a job, Lucy ___ going back to school, but she hasn’t decided yet.

A. had considered　　　 B. has been considering　 C. considered　　 　D. is going to consider

46. ----What’s that terrible noise?

　 ----The neighbors __ for a party.

　 A. have prepared　　 B. are preparing　 C. prepare　　 D. will prepare