在图7-11的超声波流量测量中，流体密度ρ=900kg/m3，管道直径D=1m，α=45°，测得Δf=10Hz，求：1）管道横截面积A；2）流体流速v；3）每秒的体积流量qV；4）质量流量qm为多少千克每秒？5）1小时的累积流量q总为多少吨？
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They ______thetrip until the rain stopped.
A. continued
B. didn’t continued
C. hadn’t continued
D. would continue
It’s ten years since we _______.
A. have parted
B. parted
C. part
D. were parted
On his next birthday he ________ married for ten years.
A. has been
B. will be
C. will have been
D. would have been
It _____ for a week and the streets were flooded.
A. has rained
B. was raining
C. had been raining
D. has been raining
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