Consider the following reaction:

$$3{\text{S}}{{\text{n}}^{2 + }}({\text{aq)}} + {\text{C}}{{\text{r}}_2}{\text{O}}_7^{2 - }{\text{(aq)}} + 2{{\text{H}}^ + }{\text{(aq)}} \to 2{\text{C}}{{\text{r}}^{3 + }}{\text{(aq)}} + 3{\text{Sn}}{{\text{O}}_2}{\text{(s)}} + {{\text{H}}_2}{\text{O(l)}}$$

Which statement is correct?

A.     ${\text{S}}{{\text{n}}^{2 + }}$ is the oxidizing agent because it undergoes oxidation.

B.     ${\text{S}}{{\text{n}}^{2 + }}$ is the reducing agent because it undergoes oxidation.

C.     ${\text{C}}{{\text{r}}_{\text{2}}}{\text{O}}_7^{2 - }$ is the oxidizing agent because it undergoes oxidation.

D.     ${\text{C}}{{\text{r}}_{\text{2}}}{\text{O}}_7^{2 - }$ is the reducing agent because it undergoes oxidation.

B