(2013·四川省乐山一模)The pupils were playing games in the classroom a gunman entered and began shooting wildly at them.
A. while
B. when
C. as
D. before
网友回答
A. while
(答案→)B. when
C. as
D. before
解析：选B 考查连词。句意：学生们正在教室做游戏，这时一名持枪的男子进来并对着他们开始疯狂扫射。连词when意为“这时”，可接短暂性动词。