单项选择题
A.体积流量相等 B.平均流速相等 C.质量流速相等 D.流速逐渐减小
A.1m/s B.2m/s C.4m/s D.0.5m/s
A.ML2T-2 B.MLT-2 C.ML-1T-1 D.ML-1T-2