53.A　 keep one's mind on sth专心做某事;keep sth in mind记住某事。

53.---Tom, keep your_____ on your studies.

　　 --- Sure, mum. I'll keep that in_____.

A. mind;mind　 B.heart;headC. brain; mind D.heart;brain

52.D course在此意为“(一)道(菜)”，“(一)盘(菜)”。

52. ---What do you think of the dinner in Mr Brown's?

---Oh, great! We have never had a better one. It's a dinner of twenty ____.

A. drinks　　 B. people　 C. tables　 D. courses

51.B wooden作定语，意为“用木头(块)制成的”，wood作定语，意为“就木头本身制成的”。从该题题干可看出，在木头上雕刻各种花样，应为wood carving。

51. His job is to sell the ____ carvings in the ____ department of the company.

A. wooden; sales B. wood; salesC. wood; saleD. wooden; sale

50.C 考名词辨异。A、B、D三个选项都是不可数名词，不可与a single连用。

50.1 haven't got a single ______from Aunt Mary since I last saw her.

A. advice　 B. news　 C. message　 D. information

49. sign与mark的区别是：sign 的意思是“迹象”、“征兆”gesture or movement made with the hand, head, etc, used to give information, a command, etc(用手或头等做出示意动作以传递信息或命令等)，mark 的意思是 written or printed symbol or figure, line etc made as signor an indication of sth(书写与印刷的符号或图、线等记号)。根据此二词的语义区别以及常识可知

48. 本题中的and连接前后两个what引导的从句，而且根据句意“他说的和他做的不一样”，可见这两个what从句的意思是各自独立的，因此谓语动词用复数形式。