單項(xiàng)選擇題

有壓恒定流水管直徑d=50mm,末端閥門關(guān)閉時(shí)壓力表讀數(shù)為21kPa,閥門打開后讀值降至5.5kPa,如不計(jì)水頭損失,則該管的通過(guò)流量Q為:()

A.15L/s
B.18L/s
C.10.9L/s
D.9L/s