Some aspects of a pilot’s job be boring, and pilots often work at inconvenient hours．
A. can; have to
B. may; can
C. have to; may
D. ought to; must
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(答案→)A. can; have to
B. may; can
C. have to; may
D. ought to; must
解析：考查情态动词。Can表示可能，have to 必须；不得不