正在值班的轮机员遇特殊情况需离开机舱,轮机长的正确做法是()。
A.指派一名能胜任者暂时替换
B.同意离开
C.随便一个人替换
D.不予理睬
参考答案:A
— He can't have finished his homework last night, ______ he?
— No. You see, he is busy doing it now. [ ]
A. has
B. may
C. can
D. did
钢材的冷加工强化有何作用意义?