18.“If not us, who? If not now, when?” these two questions are used as a.

52.Many people are（ ）to insect bites, and some even have to go to hospital.

51.（ ）at in this way, the present economic situation doesn’t seem so gloomy.

50.Firms that use computers have found that the number of staff（ ）is needed for quality control can be substantially reduced.

49.All of us would have enjoyed the party much more if there（ ）quite such a crowd of people there.

48.You（ ）Jim anything about it. It was none of his business.

47.I was very much put（ ）by Mark’s rude behavior; it really annoyed me.

46.My mother can’t get（ ）because she has rheumatism.

45.There（ ）nothing more for discussion, the meeting came to an end half an hour earlier.

44.Do help yourself to some fruit,（ ）you?

43.The central provinces have floods in some years, and（ ）.