问题补充：
Tom in the library every night over the last three months.(·北京)
A. works
B. worked
C. has been working
D. had been working
答案：
A. works
B. worked
(答案→)C. has been working
D. had been working
解析：考查时态。由句中的时间状语“over the last three months”可知应用现在完成进行时。
