50.　　 Not one in one hundred children exposed to the disease ______ likely to develop it.

a. should be　　 b. must be　　 c. is　　 d. are

49.　　 The project requires more labor( 劳动力) than ______ because it is extremely difficult.

a. has been put in　　 b. have been put in　　 c. being put in　　 d. to be put in

48.　　 In that country, the rich ______ richer, the poor, poorer.

a. become　　 b.　 has become　　 c. becomes　　 d. is becoming

47.　　 Getting to other planets or to the moon _____ many problems.

a. involve　　 b. involves　　 c. involving　　 d. to involve

46.　　 Not only the whole nation, but the whole Europe , indeed the whole human society ______ to alter its attitude to racial problems.

a. need　　 b. needs　　 c. has a need　　 d. have a need

45.　　 None of them ______ my friends.　　　 a. is　　 b. are　　 c. was　　 d. has been

44.　　 Every man, woman and child ______ some history, enough at least, to survive in the world.

a. knows　　 b. know　　 c. is known　　 d. are known

43.　　 The young ______ the vital forces in our society.

a. is　　 b. has been　　 c. are　　 d. have been

42.　　 Mathematics ______ the language of science.

a. is　　 b. has been　　 c. are　　 d. have been

41.　　 Early to bed and early to rise ______ a man healthy, happy and wise.

a. making　　 b. to make　　 c. make　　 d. makes