The school is no longer what it was 20 years ago, it was so poorly equipped.
A. when
B. which
C. since
D. where
网友回答
(答案→)A. when
B. which
C. since
D. where
解析：考查非限制性定语从句。句意“这所学校不再是20年前的样子了，那时，她的教学设备是那么的差。”根据句意可知，先行词是20 years ago，指时间，且从句不缺少成分，故用when。故选A。