Some aspects of a pilot’s job _______ be boring,and pilots often _______ work at inconvenient hours.

A．can; have to

B．may; have to

C．have to; may

D．ought to; must

小明冬天的早晨去上学，到校后觉得手很冷，根据我们学过的物理知识，请你帮他找到解决问题的2个办法，并说明这样做的物理道理．