英语学霸进来看看~有这样一道题：The girl was walking down the street_____she saw a car accident.A.while;happen B.when;happen C.while;happening D.when;to happen为什么答案是A而不是B?
问题描述：
英语学霸进来看看~
有这样一道题：
The girl was walking down the street_____she saw a car accident.
A.while;happen B.when;happen C.while;happening D.when;to happen
为什么答案是A而不是B?
答