单项选择题
A.0.41x B.0.51x C.0.61x D.0.71x
A.不锈耐酸钢无缝钢管 B.锅炉用无缝钢管 C.锅炉用高压无缝钢管 D.双面焊螺旋缝钢管
A.15m B.16m C.17m D.18m