General Principles of Oxidation-Reduction Practice Test

Consider the following oxidation-reduction reaction.

$\small \small 2K(s) + 2NH_{3}(g)\rightarrow 2K^{+}(aq) + 2NH_{2}^{-}(aq) + H_{2}(g)$

Which of the following statements is true?

$Fe(s)+O_{2}(g)\rightarrow Fe_{2}O_{3}(g)$

In the above unbalanced redox reaction, which best describes the oxidation/reduction roles of iron and oxygen?