单项选择题
A.≤0.01mmB.≤0.02mmC.≤0.03mmD.≤0.04mm
A.0.10mmB.0.15mmC.0.20mmD.0.25mm
A.开口孔隙B.封闭孔隙C.大孔隙D.小孔隙E.圆孔隙