Consider the following reaction.

$${\text{Sn(s)}} + {\text{4HN}}{{\text{O}}_3}{\text{(aq)}} \to {\text{Sn}}{{\text{O}}_2}{\text{(s)}} + {\text{4N}}{{\text{O}}_2}{\text{(g)}} + {\text{2}}{{\text{H}}_2}{\text{O(g)}}$$

Which statement is correct?

A.     ${\text{HN}}{{\text{O}}_{\text{3}}}$ is the oxidizing agent because it undergoes oxidation.

B.     ${\text{HN}}{{\text{O}}_{\text{3}}}$ is the reducing agent because the oxidation number of nitrogen changes from $+ 5$ to $+ 4$.

C.     Sn is the oxidizing agent because it undergoes reduction.

D.     Sn is the reducing agent because the oxidation number of tin changes from 0 to $+ 4$.

D