49. This is one of the means ____t he electic energy is conducted from one place to another.

A. by which　　　 　　　 B. by that　　　 　　 C. through which　　　 D. through that

48. She heard a terrible noise, ___brought her heart into her mouth.

A. it　　　　　 B. which　　　　 C. this　　　 　D. that

47. The buses, ____were already full, were surrounded by an angry crowd.

A. most of them　　 B. most of which　　　 C. which most　　　　 D. that most

46. The reason ___he didn’t come was ____he was injured.

A. that, because　　 B. why, that　　　　 C. why, because　　　 D. that, that

45. Can you solve such problems ___raised by the audience?

A. what were　　 　 B. as were　　　 C. that were　　　　 　　　　　 D. which were

44. We often think of the days ___we spent together on the island.

A. when　　　　　 B. which　　　　　 C. in which　　 　 D. during which

43. Air, _　 __we breathe every day, is around us all the time.

A. that　　　　　　　 B./　　　　　　 C. which　　　　　　　 　 D. it

42. The radio set __　 _ last week has been out of order.

A. I bought 　　 B. I bought it　　　 C. which I bought it　　 　 D. what I bought

41. He is a man of great knowledge, ___much can be learned.

A. in whom　　 　　　 B. about whom　　 　　 C. from whom　　　　 D. of whom

40. Mr. Herpin is one of the foreign experts who ___in China.

A. works　 B. is working　　　 　 C. are working　　　 　 D. has been working