单项选择题
A.≤0.030%(wt)B.≤0.035%(wt)C.≤0.040%(wt)
A.≤0.050%(wt)B.≤0.035%(wt)C.≤0.040%(wt)
A.≤0.050%(wt)B.≤0.055%(wt)C.≤0.040%(wt)