问题补充：
In order to get good marks in the coming exam, my son late every night in the past three weeks.
A. studies
B. studied
C. has been studying
D. was studying
答案：
A. studies
B. studied
(答案→)C. has been studying
D. was studying
解析：本题的关键词是时间状语in the past three weeks，该结构常常与现在完成时连用。通常与in/during the past/last+一段时间连用的句子都使用现在完成时。惊讶：在过去的3各星期里，为了在即将来临的考试中得到高分，我的儿子每天晚上都学到很晚。本句使用现在完成进行时表示动作的延续。故C正确。
