—Didn't the teacher see him entering the classroom?
—No, he on the blackboard.
A. was writing
B. had written
C. wrote
D. is writing
网友回答
(答案→)A. was writing
B. had written
C. wrote
D. is writing
解析：本题考察时态。过去进行时表示过去某一时间正在进行的动作，有延续、进行的特征。由题意知，该老师在他进来时正在写字，故选A。