—What class are they having?
—Math. Their math teacher is the classroom.
A. in the front of
B. in front of
C. on
D. behind
网友回答
(答案→)A. in the front of
B. in front of
C. on
D. behind
解析：in the front of在……的前部；in front of在……前面；on在……上面；behind在……后面。句意：他们正在上什么课？——数学。他们的数学老师在教室前部。结合语境可知选A。