（B）15. Only last month I called at .
A. my uncle B. my uncle's C. my uncles D. mine uncle
见第13题；
（C）16. The students must finish the test in .
A. three quarters of an hour time
B. three quarter's of an hour time
C. three quarters of an hour's time
D. three quarters' of an hour's time
of＋`s 的复合结构，又如：a friend of my brother`s 我兄弟的一个朋友。
（D）17. His article is better than in the class.
A. anyone's else B. anyone else C. anyone's else's D. anyone else's
（D）18. He is very tired. He needs .
A. a night rest B. rest of a night
C. a rest night D. a night's rest
's属格和of属格用法的区别：'s 表有生命的，也表时间（如上）、自然现象（如第19题）、度量衡、国家、城市；用of 表示无生命的，抽象的，或修饰语较多的；
（A）19. is covered with heavy snow.
A. The earth's surface B. The surface of earth
C. The surface earth D. The earth surface
（A）20. This question is too difficult, and everyone is to solve it.
A. at his wits' end B. at one's wits end
C. in his wits' end D. out of his wits end
固定词组，必须用 's . 如第20题：不知所措，又如：in one's mind's eye 在某人的心目中
