问题补充：
—What were you doing at this time yesterday?
—We in the classroom.
A. read
B. were reading
C. are reading
D. was reading
答案：
A. read
(答案→)B. were reading
C. are reading
D. was reading
解析：句意：昨天这个时刻你们正在做什么？——我们正在教室里面读书。结合语境可知下文描述的是过去某时正在进行的动作，结合语境可知选B。
