单项选择题
A.1200℃ B.1250℃ C.1300℃ D.1350℃
A.2% B.1.8% C.1.2% D.0.8%
A.48%~51% B.60% C.70% D.80%
A.<7% B.<7.5% C.<8% D.<8.5%
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