The school has developed an online systemstudents can choose their own teachers.A. whichB

问题补充：

The school has developed an online systemstudents can choose their own teachers.

A. which

B. that

C. whom

D. where

答案：

A. which

B. that

C. whom

(答案→)D. where

解析：考查定语从句：句意：学校已经开发了一个在线系统，里面学生可以选择自己的老师。这是定语从句，先行词是an online system，定语从句中缺少的是地点状语，选D。