问题补充：
He his work, otherwise, he wouldn’t be enjoying himself by the seaside.
A. must have completed
B. should have completed
C. ought to complete
D. must complete
答案：
(答案→)A. must have completed
B. should have completed
C. ought to complete
D. must complete
解析：句意：他一定是完成了他的工作，否则他不会在海边玩得那么开心。A. must have completed对过去的肯定推测；B. should have completed本应该完成，实际上没完成；C. ought to complete应该完成；D. must complete必须完成。表示对现在的推测。故选A。
考点: 考查情态动词表推测的用法。
