题干
While we _______ football in the classroom, the teacher came in.
A：were play
B：were playing
C：are playing
D：played
答案(点此获取答案解析）
B
While we _______ football in the classroom, the teacher came in.
A：were play
B：were playing
C：are playing
D：played
的图象与函数y＝2sinπx(－2≤x≤4)的图象所有交点的横坐标之