单项选择题
A.进气门0.25-0.30mm，排气门0.30-0.35mm B.进气门0.30-0.35mm，排气门0.25-0.30mm C.进气门0.20-0.25mm，排气门0.30-0.35mm D.进气门0.15-0.20mm，排气门0.30-0.35mm
A.变形 B.表面碰伤 C.磨损 D.裂纹
A.曲轴两端主轴颈 B.中间一道主轴颈 C.曲轴两端顶针孔 D.任意两道主轴颈