50. Not until the early years of the 19th century______ what heat is.

A. man did know　　　 B. man knew　　　　 C. didn’t man know　　 D. did man know

49. _____ he realized it was too late to return home.

　A. No sooner it grew dark than　　　　　 B. Hardly did it grow dark when

　C. It was not until dark that　　　　　 D. It was until dark that

48. So little _____ agree on the plan that they could not settle their difference.

　A. did they　　　　　 B. do they　　　　 C. they did　　　 D. they did not

47. We were lucky enough， for no sooner _____ home _____ it rained.

　A. we returned， and　　　 　　　　　　　B. we had returned， when

　C. did we return， when　　　　　　　　 D. had we returned， than

46. ____， he would have passed the exam.

　A. If he were to study　　　　　　　　　 B. If he studied hard

C. Had he studied hard　　　　　　　　　 D. Should he study hard

45. Little wonder _____ up their hands in dismay.

　A. have some thrown　 B. some have thrown C. thrown some have D. have thrown some

44. No sooner ____ they rushed out into the street.

　A. did they hear the news than　　　　　 B. did they hear the news when

　C. had they heard the news than　　　　 D. had they heard the news when

43. Well ____ know him and well ____ know me.

　A. I did， he did　　 B. did I， he did　C. did I， did he　 D. I did， did he

42. Little _____ about his own health though he was very ill.

　A. he cared　　　　　 B. did he care　　 C. he cares　　　 　 D. does he care

41. So carelessly _____ that he almost killed himself.

　A. he drives　　　　　 B. does he drive　C. did he drive　　 D. he drove