Within the cell it is important to prevent mixing or direct contact of

 The cell it is important to prevent mixing or direct contact of ${\mathrm{MnO}}_4^{-},{\mathrm{Fe}}^{2+}$.

An electrochemical cell is a structure that may produce electrical energy from chemical processes taking place inside of it or utilize external electrical energy to speed up chemical reactions taking place inside of it.

Hence the option A is correct.