问题补充：
--- Where is Jack?
--- He football on the playground with those AFS students, but I am not sure.
A. must be playing
B. must have played
C. may be playing
D. may have played
答案：
A. must be playing
B. must have played
(答案→)C. may be playing
D. may have played
解析：可联系答.案.网客服索取。
