Suddenly I woke up. I was confused and didn’t know where I was.
A. I have been dreaming
B. I had been dreaming
C. I have dreamed
D. I had dreamed
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“ Is David still here?” “No, I am afraid he isn’t. He___________ about 10 minutes ago.”
A. has left
B. has been leaving
C. left
D. was left
I went to Sue's house, but she wasn't there.
A. She went out
B. She has gone out
C. She had gone out
D. She had been going out.
We were extremely tired at the end of the journey. ________ for more than 24 hours.
A. We have travelled
B. We have been travelling
C. We had travelled
D. We had been travelling
当平衡阀的阻力系数增大时，阀门的流量G（ ）
A. 增大
B. 减小
C. 不变
D. 以上都不对
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