It’s very important for a student to ________ a good state of mind while taking the college entrance examination.

A．keep out

B．keep on

C．keep up

D．keep off

关于“气”与“汽”的叙述不正确的是()

A．呈气态的物质温度在临界温度以下的称为汽

B．呈气态的物质温度在临界温度以上的称为气

C．气表示单纯依靠压缩不能使它液化

D．汽与气没有区别

E．汽表示单纯依靠压缩不可以使它液化