单项选择题
A.430℃ B.450℃ C.480℃ D.400℃
A.2% B.4% C.6% D.8%
A.0.1% B.0.2% C.0.5% D.1%
A.氢蚀 B.氢脆 C.生成硫化氢 D.60%
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