41. The United States is composed of fifty states， two of _____ are separated from the others by land or water.

A. them B. that

C. which D. those

42. They did not discover until later _____ the car had been destroyed.

A. as B. than

C. which D. that

43. They overcame all the difficulties and fulfilled the plan ten days ahead of schedule， _____ was something we had not expected.

A. that B. this

C. it D. which

44. That‘s the reason _____ Ann could not do her part of the job.

A. that B. of

C. because D. why

45. The company official _____ I thought would be fired received a raise.

A. whom B. whoever

C. who D. of whom

46. In 1990 he caught a serious illness from _____ effects he still suffers.

A. that B. which

C. what D. whose

47. His brother had become a teacher， _____ he wanted to be.

A. who B. what

C. which D. that

48. My vacation begins next Tuesday， _____ I will leave for Flofida.

A. which B. that

C. while D. when

49. He has made another wonderful discovery， _____ of great importance to science.

A. which I think it is B. of which I think is

C. I think which is D. which I think is

50. I decided to buy a car because we had sold _____ we had in England before leaving.

A. that B. the other

C.which D. the one