In the redox reaction

$2{\text{MnO}}_4^{-}+5{\text{C}}_2{\text{O}}_4^{2-}+16{\text{H}}^{+}\rightleftharpoons 2{\text{Mn}}^{2+}+10{\text{CO}}_2+8{\text{H}}_2\text{O}$

The ion acting as autocatalyst is

• A

  ${\text{MnO}}_4^{-}$

• B

  ${\text{C}}_2{\text{O}}_4^{2-}$

• C

  ${\mathrm{H}}^{+}$

• D

  ${\text{Mn}}^{2+}$