单项选择题
A.锈点范围B.锈点直径C.保护层厚度D.蚀余厚度
A.摸B.看C.量D.照
A.5B.4C.3D.2
A.10g/L,15g/LB.10g/L,20g/LC.15g/L,20g/LD.20g/L,20g/L
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