解析：独立主格做状语。主语concert 不可能执行take the seat 这一动作，必须加the listeners 做逻辑主语

15. ---- Yoshouldn’t have gone there alone last night.

---- But I ______, because Xiao Wang went there, too.

A. didn’t B. had to C. did D. should

解析：表过去的事实。

16. ---- There is a lot of smoke coming out of the teaching-building there.

---- Really? It _____ be a fire, most probably.

A. can B. ought to C. have to D. must

解析：从most probably.可以看出是很可能, must表示一定

17. If yodon’t wait _______ the red light, yowill be punished by the policeman.

A. at B. under C. for D. on

解析：at 意为“看见”

18. ________ doesn’t seem to have been much difficulty in solving the problem.

A. It B. That C. There D. He

解析：这是There be句型一种比较复杂的表现形式，由下列各句逐步形成：

There is much difficulty in solving the problem.

There seems to be much difficulty in solving the problem.

There seems to have been much difficulty in solving the problem.

There doesn’t seem to have been much difficulty in solving the problem.

E.g. There used to be a big tree in front of the old house.

There happened to be a foreign teacher there.

There is said to be no life on the moon.

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.