The school has developed an online system students can choose their own teachers.
A. which
B. when
C. that
D. where
网友回答
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。