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【单选题】
关于调节阀和变频器,下列说法正确的是( )A.
调节阀调节流量是改变了管路系统的阻力系数，阀门开度越小，阻力损失越小，耗能越小
B.
变频器是改变电机的转速调节流量，转速越小，流量越大
C.
变频器是改变管路的阻力来调节流量的
D.
调节阀开度减小，消耗在调节阀上的能量增大，是消耗流体的能量来调节流量
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举一反三
【单选题】Speaker A: Sorry,I am late.I miss the bus. Speaker B:
A.
I won’t forgive(原谅)you.
B.
It’s OK. But you’d better go out earlier next time:
C.
Yes, it is.
【单选题】—Would you like to play tennis with me _________ it doesn’t rain tomorrow? —Sure, _________ I am busy.
A.
if; since
B.
whether; but
C.
if; unless
D.
because; until
【简答题】It's time to go home now. I am on a bus on a rainy day, and a woman with a dog gets on the bus. It is a big dog and its feet (脚) are not clean. I don't want the dog to sit next to me. But the woman s...
【简答题】I am ___a bus/metro, and I am getting ready to get ___. I am ___a taxi, and I am getting ready to get ___.
【单选题】听力原文： Hello, I was once a hostess. Now I am on my lust bus trip and I'm quite surprised at the services offered during the trip. The services they offered includes meals on the way, rest rooms and pub...
A.
By bus.
B.
By air.
C.
By train.
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