单项选择题
A.350 B.400 C.450 D.500
A.0.5%~0.6% B.0.6%~0.8% C.0.85%~1.05% D.1%~2%
A.1 B.5 C.10 D.15
A.射流 B.稳流 C.层流 D.紊流
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