The clever boy made a hole in the wall, ________ he could see what was going on inside the building.

The clever boy made a hole in the wall, ________ he could see what was going on inside the building.

A.on which

B.at which

C.through which

D.in which

答案及解析： C

这题考查定语从句：介词+which，句意是：聪明的男孩在墙上打了个洞，通过这个 洞他可以看到大楼里发生的事。选C。