单项选择题
A.1.8m/s B.2.0m/s C.2.2m/s D.0.6m/s
A.1.8m/s B.1.5m/s C.2.2m/s D.0.6m/s
A.2m/s B.1.8m/s C.2.2m/s D.1.6m/s
A.46000m3/h B.42000m3/h C.18000m3/h D.12000m3/h
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