已知d1＝100mm，d2＝200mm，υ1＝4m/s，管道突然扩大的水头损失为()。
A. 0.46mH2O
B. 0.52mH2O
C. 0.58mH2O
D. 0.62mH2O
输沙率的单位为()。
A. kg/h
B. m3/min
C. m/s
D. kg/s
What is special about the rock climbing competition？
A foreign team takes part in it.
B. You can watch it without paying.
C. You don't have to be a sportsman to take part.
D. The bus trip to the place of the competition is free.
What does the word "They" in "They can probably pay a certain part of the full price..."refer to？
A. People.
B. Shops.
C. Goods.
D. Catalogue.
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