问题补充：
Can you think of some casesdrivers obviously knew the traffic rules but didn’t obey them?
A. why
B. where
C. as
D. which
答案：
A. why
(答案→)B. where
C. as
D. which
解析：此题考查定语从句。理解case的含义是”关键”，case在此表示”情形，境况”,故选where 充当定语从句的状语，而which在从句中不能充当状语，故不能选which。
