单项选择题
A.20°~60°B.50°~100°C.60°~120°D.80°~160°
A.主轴颈与轴瓦B.连杆轴颈与轴瓦C.凸轮轴与轴套D.活塞和活塞环与汽缸壁
A.15%~20%B.35%~40%C.55%~60%D.75%~80%