45. ____ seems easy in theory seems difficult in practice.

　　A. That B. With C. What D. It

　　46. The house is dark; the Browns_____ to bed.

　　A. may go B. should go

　　C. should have gone D. must have gone

　　47. This is a mistake which is typical ____ beginners.

　　A. for B. of C. to D. with

　　48. There may be, somewhere outside the solar system, intelligent life ____ messages to us.

　　A. sends B. sent C. sending D. has sent

　　49. Please be sure to telephone me the next time you____.

　　A. will ***e B. would ***e C. shall ***e D. ***e

　　50. All the machines____ by the end of the following week.

　　A. were repaired B. will be repaired

　　C. have been repaired D. will have been repaired

　　51____ is well known, light, like heat, is a form of energy.

　　A. It B. what C. Just as D. As

　　52. You should turn off all the water tonight ____ freezes and the pipes burst.

　　A. in some cases it B. in case it C. in that case it D. in any case it

　　53. Music often____ us of events in the past.

　　A. reminds B. memorizes C. remembers D. reflects

　　54. He didn't know I was in his office. He was too busy to____ me.

　　A. pay attention to B. notice C. know D. realize

　　55. Does it____ much to have the bicycle repaired?

　　A. pay B. spend C. cost D. ask

　　56. You should act _____ the advice of your doctor.

　　A. to B. on C. at D. as

　　57. There was a teapot fashioned like a China duck, out of ____ open mouth the tea was supposed to ***e

　　A. which B. its C. that D. whose

　　58. Beijing is now busy___ the Olympic Games which is to be held in the year 2000.

　　A. preparing for B. prepared for C. to prepare for D. prepare for

　　59. The scientist didn't mind ____and went on with his investigation.

　　A. laughing at B. to be laughed at

　　C. being laughed at D. laughed at

　　60. If you____ that late movie last night, you wouldn't be so sleepy.

　　A. hadn't watched B. haven't watched

　　C. wouldn't have watched D. didn't watch