20．D。本句说明这个工人回答彼得的问题之前沉默了一会儿。A选项应用a moment； C选项表示某一点时间； D选项表示一段时间或一会儿，为正确选项。

21

A strange thing happened to Henry yesterday. He was on a bus and to __1__. So he stood up and rang the bell. __2__ make sure the driver heard him, he rang it twice, but the bus __3__ stop. And the conductor came and shouted __4__ him.

The conductor was __5__ angry and spoke __6__ fast that Henry didn’t understand __7__. The bus stopped at the next bus and Henry got off. As he got off he heard someone said, “ I think he __8__ a foreigner.”

When Henry got __9__, he told his wife about it.

“ __10__ times did you ring the bell?” his wife asked.

“ Twice,” said Henry.

“ Well, that’s the signal (信号) __11__ the driver __12__ on.” His wife explained, “only the conductor __13__ to ring the bell twice. That’s why the conductor __14__ so angry!”

Henry nodded(点头). “ __15__,” he said.

19．B。根据句中否定词not 及文意应选anyone。

18．C。因为今天是彼得最后一天上班说明明天他就要退休retire。

17．C。“on the job”为一常用短语。意为“执行公务”。

16．C．这里应选择一个介词构成介词短语在句中做状语。介词past 表“经过”； across 强调“从一边到另一边”；而into 表示“进入到……里面”。 根据文意across应为正确选项。

15．D。tell, order后面应直接接人作宾语表示告诉某人和命令某人，而用say应为say to sb. 故said为正确选项。

14．D。“as usual”为固定短语，意为“象平常一样”。

13．A。习惯用语look through 意为“彻底检查”。

12．C。固定结构be able to do sth. 意为“能够干某事”。

11．B。四个选项从语法上讲都可以，只能从文意上进行区分，smuggling意为“走私”，是正确选项。