问题补充：
－Have you known the exam result?
－Not yet. I guess the paper by the teacher now.
A. has graded
B. is graded
C. is being graded
D. is grading
答案：
A. has graded
B. is graded
(答案→)C. is being graded
D. is grading
解析：句意：--你知道考试结果了吗？--还没有，我猜试卷正在被老师批改。因为时间是now，而且paper和grade是被动关系，用现在进行时的被动语态，所以选C。
