单项选择题
A.≤0.050%(wt)B.≤0.055%(wt)C.≤0.040%(wt)
A.≤0.070%(wt)B.≤0.055%(wt)C.≤0.065%(wt)
A.≤0.050%(wt)B.≤0.055%(wt)C.≤0.045%(wt)