选择题:31. The pilot asked all the passengers on board to

题目内容:
31. The pilot asked all the passengers on board to remain _____ as the plane was making a landing.(本题1.0分)
A、 seat
B、 seating
C、 seated
D、 to be seating
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4. (判断题) 无论层流还是紊流中,沿程水头损失都与平均流速的平方成正比。( )(本题2.0分)

4. (判断题) 无论层流还是紊流中,沿程水头损失都与平均流速的平方成正比。( )(本题2.0分) A、 正确 B、 错误

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46. (判断题) 已知某管流的雷诺数ex_1257577846586_0.gif,则其相应的断面平

46. (判断题) 已知某管流的雷诺数ex_1257577846586_0.gif,则其相应的断面平均流速与最大流速之比ex_1257577868680_0.g

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