What's your brother?[ ]
A. He is a boy.
B. He is twelve.
C. He is a student.
答案:C
分馏法原油稳定装置轻烃(气态和液态)管道和容器要用()进行置换。
A.氧气
B.氢气
C.氮气
D.水
进入水泥库时,下灰工首先负责什么?