问题补充：
—Tony, you must have noticed the student who broke the glass.
—Im sorry.Iattentively.
A. studied
B. was studying
C. am studying
D. would study
答案：
A. studied
(答案→)B. was studying
C. am studying
D. would study
解析：考查动词的时态。由答话人说“对不起”可知，当有人打碎玻璃时，他正在专心致志地学习，没有看到打碎玻璃的人。故使用过去进行时表示过去某一时间正在做某事，所以答案为B。
