When $\text{K}_2\text{MnO}_4$ is added to water, this reaction takes place: $a\,\text{MnO}_4^{2-}(aq) + b\,\text{H}_2\text{O}(l) \rightarrow c\,\text{MnO}_4^{-}(aq) + d\,\text{MnO}_2(s) + e\,\text{OH}^-(aq)$. What are the values of $a$ and $c$ in the balanced chemical equation?
- A$a=2,\ c=1$
- B$a=3,\ c=2$
- C$a=4,\ c=3$
- D$a=5,\ c=4$