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?