问题补充：
There are many tall trees our classroom.
A. in the front
B. in front
C. in front of
D. in the front of
答案：
A. in the front
B. in front
(答案→)C. in front of
D. in the front of
解析：本题的含义是在教室前面有许多的高大的树木，树应该在教室外面的前面，表示在外部前面通常用in front of，内部前面用in the front of，后面没有名词用A或B，故选C。
