A

 B

 C

 D

 方案

 现象

 热水中未燃烧的白磷在通入氧气后燃烧

 点燃某气体后，干冷烧杯内壁出现无色液滴，澄清石灰水变浑浊

 黄铜片能在铜片上刻画出痕迹

 水中的铁钉生锈，植物油中的铁钉没生锈

结论

 燃烧需要氧气

 该气体就是甲烷（CH₄）

 合金的硬度比组成它的纯金属小

 铁生锈只需要与氧气接触

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Tel: 010—69191617