问题补充：
Mary sits the classroom and I sit her.
A. in the front of, in the front of
B. in front of, in front of
C. in the front of, in front of
D. in front of, in the front of
答案：
A. in the front of, in the front of
B. in front of, in front of
(答案→)C. in the front of, in front of
D. in front of, in the front of
解析：句意：玛丽坐在教室的前部，我坐在她的前面。这两个词组都是“在……前面”的意思，但他们之间有一些区别，in front of, 指物体外部的前面，in the front of指物体内部的前面，即在参照物的里面。根据句意，故选C
