$H_2O_2$ acts as a reducing agent in

• A
  $2 NaOCl + H_2O_2 \rightarrow 2 NaCl + H_2O + O_2$
• B
  $2 Fe^{2+} + 2 H^{+} + H_2O_2 \rightarrow 2 Fe^{3+} + 2 H_2O$
• C
  $Mn^{2+} + 2 H_2O_2 \rightarrow MnO_2 + 2 H_2O$
• D
  $Na_2S + 4 H_2O_2 \rightarrow Na_2SO_4 + 4 H_2O$