There must have been something wrong with the machine.

19. Are the parents who let their child who is ______ walk in the dark alone at night considerate?

A. young enough B. too young to C. not old enough to D. so young

解析：分析句子结构，who is so young 在句为修饰的定语,另有let sb.do sth.

20. If yowant to sell your product yomust _____ it.

A. advertise B. advertise for C. advertise on D. advertise to

解析：advertise sth. 为……登广告， 登广告宣传…… advertise for sth.(sb.)登广告征求或寻找某物或某人

比较：advertise jobs 登广告招人 advertise for jobs 登广告求职

21. ----Any news about Bill Clinton?

----He left power three years ago and has a little now and a little then been ______.

A. heard of since B. heard since C. heard before D. heard of before

解析：答句可改为I have heard of him a little now and a little then since he left power three years ago.→

He has a little now and a little then heard of since he left power three years ago.

22. Professor Lihas ________ teach psychology since he came to the Central China Normal University.

A. determination to B. been determined to C. been determining to D. determined to

解析：Since引导的时间状语从句强调主句谓语动词动作的持续性。

23. The idea for the new machine came to Mr. Baker ______ to his invention recently.

A. while devoting B. while devoted C. while he was devoted D. while devoting himself.

解析：while后主语及助动词不能省略，因为两句主语不一致

Mr Baker thought of the idea for the new machine (B / D) to his invention recently.

24. How many of us ______ a meeting that is not important to us would be interested in the discussion?

A. attended B. attending C. to attend D. have attended

解析：attending a meeting that is not important to us做定语

25. I can _____ some noise while I’m studying, but I can’t stand very loud noise.

A. put up with B. get rid of C. have effects on D. keep away from

解析：从后面的stand可以推断，这里用put up with 表示忍受

26. Before leaving home, make sure to turn off the electricity, lock the door, ______ the windows open.

A. and not to leave B. instead of leaving C. rather than leave D. and not leave

解析：lock和 turn都是不定式肯定形式lock 前省略了to ,但not to leave 是否定形式，to不可省

27. A mysterious illness, referred to as “ a typical phenomena”, has been brought under control, the government said on Wednesday, ______ no cause of it has been made public.

A. though B. when C. that D. because

解析：“尽管”没有病例公布

28. Space exploration has been made ______ with the development of modern science and technology.

A. it possible B. it was possible C. that possible D. possible

解析:该句测试是make sb./ sth.+adj. 结构，如果用A项，后应用to do sth.，因为it是形式宾语，代替不定式。

With the development of modern science and technology, man has made space exploration possible.

29. We want such materials ________ can bear high temperature and pressure.

A. that B. as C. what D. which

解析such materials as 引导的是定语从句,as 在从句中作主语;而such materials that 引导的是结果状语从句，that 在从句中不充当成分。

30. Hardly ___________the door when he rushed into the office out of breath.