单项选择题
A.O形密封环 B.金属密封环 C.密封牛皮碗 D.密封橡胶碗
A.φ1.0mm B.φ0.8mm C.φ0.5mm D.φ1.2mm
A.φ1.0mm B.φ0.8mm C.φ0.5mm D.φ0.2mm