问题补充：
—Has William finished writing his graduation paper yet?
—I don’t know exactly，but he all day.
A. is writing
B. has been writing
C. was writing
D. wrote
答案：
A. is writing
(答案→)B. has been writing
C. was writing
D. wrote
解析：表示“一整天都在做某事(此时该动作还没有结束)”要用现在完成进行时。
