问题补充:
He fell off the bike .
A. while he rode
B. while he was riding
C. while he is riding
D. while on bike
答案:
A. while he rode
(答案→)B. while he was riding
C. while he is riding
D. while on bike
解析:本题主要考查的是while 引导的时间状语从句,一般而言,主句的动作发生在从句之中,故从句要用进行时态,故选B