控制元件的功能是
A. 控制和调节压缩空气的压力
B. 控制和调节压缩空气的流量
C. 控制和调节压缩空气的方向
D. 以上都不对
I must hurry. My friend will be annoyed if __________ on time.
A. I am not
B. I be not
C. I will be not
D. I will not be
I didn't realize that Gary was in hospital. If __________ he was in hospital, I would have gone to visit him.
A. I have known
B. I had known
C. I knew
D. I know
A: What shall we do tomorrow? B: Well, if __________ a nice day, we will go to the beach.
A. it is
B. it be
C. it will be
D. it was