A.4B.6C.8D.9
A.對(duì)稱(chēng)式螺紋B.對(duì)數(shù)式螺紋C.非對(duì)稱(chēng)式螺紋D.非對(duì)數(shù)式螺紋
A.CDRB.PATC.PPTD.PCT