顺义区中信银行:求救!HELP!!!!!!!!!!!!!!!!!!!!!!!!!!

18.“Time is running out,______?” a. hadn't we better got start b. hadn't we better get start b. hadn't we better get started d. hadn't we better not started 20.The students in the classroom ______ not to make so much noise. a. need b. ought c. must d. dare 21.You ______ last week if you were really serious about your work. a. ought to come b. ought to be coming c. ought have come d. ought to have come 24.“Tom graduated from college at a very young age.” “He ______ have been an outstanding student.” a. must b. could c. should d. might 25.You ______ the examination again since you had already passed it. a. needn't have taken b. didn't need to take c. needn't take d. mustn't take 26.He is really incompetent! The letter ______ yesterday. a. should be finished typing b. must be finished typing b. must have finished typing c. should have been finished typing 27.The boy told his father that he would rather ______ an astronaut. a. become b. to become c. becoming d. became 28.When we reached the station, the train had still not arrived; so we ______. a. needed not to hurry b. needn't have hurried b. need not to have hurried d. didn't need to hurry 30.He was afraid what he had done ______ a disastrous effect on his career. a. might have b. could be c. have been d. shall be
为什么原因?????????