1. It may be necessary to stop__________________________(每隔...时间) in the learning process and go back to the difficult points in the lessons.

　　2. The mad man was put in the soft-padded cell lest he ______________(伤害自己).

　　3.Jean did not have time to go to the concert last night because she was_______________(忙着准备) her examination.

　　4. The ship's generator broke down and the pumps____________________(不得不用手工操作) instead of mechanically.

　　5. Why didn't you tell me you could me the money? I___________________________ (本来不必从银行借钱的) 221

　　参考答案：

　　1. at intervals

　　2. injure himself

　　3. busy preparing for

　　4. had to be operated manually

　　5. needn't have borrowed it from the bank.