A.45° B.9O° C.75° D.180°
A.0.2~0.4mm B.0.4~0.6mm C.0.6~0.8mm D.小于0.2mm
A.葉輪的形狀 B.葉輪的直徑大小 C.輪轂的厚度 D.葉片的高度