( ) We were walking along the river _____ it suddenly began to rain.A.as B.while C.when D.then
问题描述：
( ) We were walking along the river _____ it suddenly began to rain.A.as B.while C.when D.then
答
C
be doing when 正要干某事,突然.
B连接两个长动作,排除,D语意错误
A没有be doing as的结构
【俊狼猎英】