5.C。amount 与不可数名词连用;number与可数名词连用; B、D不符合题意。

4.A。in a ...mood 处于……的心境, 心情。

3.D。商店出售儿童服装和妇女服装,不是两者共有之物,故应选D。　　　　

2.D。students of mathematics相当于mathematics students。

1.A。表示时间、地点、称呼等的名词常直接用作定语,修饰另一名 词。如:afternoon tea(下午茶);evening school(夜校); country life(乡村生活);winter sleep(冬眠)。另外,表示类别、用途、材料、功能、来源等的名词也常直接用作定语。如: government office(政府办公室);history lesson(历史课);women drivers(女司机);shoe store(鞋店);tooth brush(牙刷);meeting room(会议室)等。

50. Things of ____ kind come together; people of a mind fall into ____ same group.

　　 A. a; a　　　　　　　　　 B. a; the　　　　　　 C. the; the　　　　 D. the; a

答案及简析：

49. I don’t know who invented ____ telescope, but I think it is ____ most useful invention.

　　 A. the; the　　　　　　　 B. the; a　　　　　　 C. a; the　　　　 D. a; a

48. According to the recent reports, one of the rare animals, ____ crocodile, is in ____ danger of dying out.

　　 A. the; the　　　　　　 B. the; /　　　　　　　 C. / ; /　　　　　 D. / ; the

47. The soldier was wounded in ____, but he caught the enemy officer by____.

　　 A. the knee; the arm　　　　　　　　 B. his knee; his arm　

　　 C. his knee; the arm　　　　　　　　 D. the knee; his arm

46. When we study a globe, we can see ____ is the largest ocean and ____ the largest continent.

　　 A. the Pacific; Asia　　　　　　　　　 B. Pacific; the Asia　　　　

　　 C. the Pacific; the Asia　　　 　　　　D. Pacific; Asia