单项选择题
A.氧 B.氯 C.氮 D.碳
A.10.7% B.1.07% C.11.7% D.1.17%
A.5 B.7 C.10 D.12
A.3.1~3.9 B.3.0~4.4 C.3.9~5.1 D.5.1~7.8
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