问题补充:
The school has developed an online system students can choose their own teachers.
A. which
B. when
C. that
D. where
答案:
A. which
B. when
C. that
(答案→)D. where
解析:句意:学校研发了一个网络系统,在这一系统中学生可以选择自己的老师。这里是定语从句先行词是online system,where在从句中作地点状语,其他的关系词不能作地点状语,故选D。