填空题 The ship’s generator broke down and the pumps（）(不得不用手工操作) instead of mechanically.

填空题 It may be necessary to stop（）(每隔一定时间) in the learning process and go back to the difficult points in the lessons.

填空题 There’s a man at the reception desk who seems very angry and I think he means（）(想找麻烦).