板坯中C.Mn、()元素含量的增加会导致轧制负荷的增加。
参考答案:Nb
– I’m leaving for Beijing next week.
– How long ______ there?
A.have you stayed
B.are you staying
C.had you stayed
D.did you stay
装卸烟叶时要轻拿轻放,不能摔丢烟包。