Usually there is a blackboard on the front wall in the classroom there is a slogan.A. abo

问题补充：

Usually there is a blackboard on the front wall in the classroom, there is a slogan.

A. above which

B. in that

C. on which

D. from that

答案：

(答案→)A. above which

B. in that

C. on which

D. from that

解析：这是一个非限制性定语从句，从句中缺少地点状语，用介词+which，不能用that，故排除BD；on表示某物在另一物体的表面上并与该物体接触；over表示某物在另一物的上方，不与该物体接触，根据句意标语应在教室的上方，故选A。