除油罐投运时，应先打开罐底及收油槽内的（）阀门。
A.排污
B.溢流
C.伴热
D.置换
参考答案：C
--- How do you like your math teacher?
--- She is strict __________us.
A. with B. in C. at
CO2灭火剂的作用是（）
A.冷却
B.窒息
C.稀释
D.A+B
