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？
