Answer the following question given this paragraph: 

Reaction with Elements Oxygen reacts directly at room temperature or at elevated temperatures with all other elements except the noble gases, the halogens, and few second- and third-row transition metals of low reactivity (those with higher reduction potentials than copper). Rust is an example of the reaction of oxygen with iron. The more active metals form peroxides or superoxides. Less active metals and the nonmetals give oxides. Two examples of these reactions are: 2Mg(s) + O 2(g) ⟶ 2MgO(s) P 4(s) + 5O 2(g) ⟶ P 4 O 10(s) The oxides of halogens, at least one of the noble gases, and metals with higher reduction potentials than copper do not form by the direct action of the elements with oxygen.


Q: Rust is an example of the reaction of oxygen with what?


A:
iron