What is the reducing agent in the reaction below?

$$2{\text{MnO}}_4^ - ({\text{aq)}} + {\text{B}}{{\text{r}}^ - }({\text{aq)}} + {{\text{H}}_2}{\text{O(l)}} \to {\text{2Mn}}{{\text{O}}_2}{\text{(s)}} + {\text{BrO}}_3^ - ({\text{aq)}} + 2{\text{O}}{{\text{H}}^ - }({\text{aq)}}$$

A.     ${\text{B}}{{\text{r}}^ - }$

B.     ${\text{BrO}}_3^ -$

C.     ${\text{MnO}}_4^ -$

D.     ${\text{Mn}}{{\text{O}}_{\text{2}}}$

A