You pay your library fines. If not, you not be allowed to graduate.
A. may; should
B. should; need
C. must; will
D. will; can
网友回答
A. may; should
B. should; need
(答案→)C. must; will
D. will; can
解析：第一空可以用should或must，表示根据规定“应该；必须”，第二格只能用will，表示对目前或将来情况的推测。