问题补充：
trees have been planted near here, so the air is very fresh.
A. Two hundreds
B. Hundred of
C. Hundreds of
D. Hundreds
答案：
A. Two hundreds
B. Hundred of
(答案→)C. Hundreds of
D. Hundreds
解析：
试题分析: 句意：成百上千棵树已经种在这儿附近了，所以空气非常新鲜。hundred百，前加数字时不加s，表具体的数目；后接of时加s，表成百上千的，故选C
