Thepurposeofpressurecontrolis to ()
A. determine direction
B. determine speed
C. determine force
D. alloftheabove
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I would like to ______(订一张票)for Paris, please.
We have _________(有座位)on fligt leaving Shanghai at 9 o'clock.
Would you prefer first class, business or ________(经济舱)?
Please arrive at the airport two hours before ______(起飞时间) to check in.