单项选择题
A.≥7B.≤8C.≤10D.≤12
A.10mg/LB.1mg/LC.0.1mg/LD.0.001mg/L
A.≤2mg/LB.≤3mg/LC.≤5mg/LD.≤10mg/L
A.苛性脆化B.汽水共腾C.结垢D.腐蚀
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