(2005年)A、B两点之间并联了三根管道，则AB之间的水头损失hfAB等于( )。
A. hf1+hf2
B. hf2+hf3
C. hf1+hf2+hf3
D. hf1=hf2=hf3
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Questions 12 to 15 are based on the conversation you have just heard.
A. Her car is badly damaged by the driver.
B. The driver is totally drunk and overspeed.
C. The drivers" behavior is beyond control.
D. He seems not to be focused enough.
Questions 22 to 25 are based on the passage you have just heard.
A. One of the dormitory buildings will be used as an office building.
B. No one is allowed to live off campus.
C. There will be more freshmen admitted this year.
D. The dorms on north campus will be closed for repair.
Questions 19 to 21 are based on the passage you have just heard.
A. They used to treat customers with enthusiasm and patience.
B. They have been always considerate to customers.
C. They still remain indifferent to customers today.
D. They are responsive to customers today.
(2009年)正常工作条件下的薄壁小孔口与圆柱形外管嘴，直径d相等，作用水头H相等，则孔口流量Q1和孔口收缩断面流速V1与管嘴流量Q2和管嘴出口流速V2的关系是( )。
A. V1＜V2，Q1＜Q2
B. V1＜V2，Q1＞Q2
C. V1＞V2，Q1＜Q2
D. V1＞V2，Q1＞Q2
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