Answer: C. iron oxide
Explanation:
In a chemical reaction , the reactants are written on the left hand side followed by a rightarrow and then products are given on the right side of the arrow.
In the given chemical equation :
[tex]4Fe+3O_2\rightarrow 2Fe_2O_3[/tex]
Reactants are iron (Fe) and oxygen [tex](O_2)[/tex] and product is iron oxide [tex](Fe_2O_3)[/tex].