The girls a game called Bomb happily when the teacher suddenly entered the classroom.
A. played
B. were playing
C. are playing
D. had played
网友回答
A. played
(答案→)B. were playing
C. are playing
D. had played
解析：考查时间状语从句。根据entered可知，主句应该用过去时，排除C、D。句意“那些女孩正在玩一种叫‘Bomb’的游戏，当老师突然走进教室的时候。”根据句意可知，主句应该用进行时。故选B。