单项选择题
某螺旋桨半径为2m,在其中一桨叶上0.3R、0.6R、0.9R处各旋转36°时分别测得量杆的升程为256mm、252mm、260mm,请问
A.260mm B.2600mm C.252mm D.2520mm
A.252mm B.2520mm C.178mm D.1780mm
A.256mm B.2560mm C.252mm D.1780mm