There is a blackboard_the wall and there are two doors_the wall.

问题描述:

There is a blackboard_the wall and there are two doors_the wall.
a.on,on b.in,in c.on,in d.in,on

C 考查介词的用法,挂在墙上的东西用介词on,在墙上和墙构成一个整体的东西用in.例如:there are two holes in the wall.