Which is necessary for the conversion of butan-2-one into propanoic acid?

• A

  Tollen’s reagent

• B

  Fehling solution

• C

  ${\text{NaOH/I}}_{\text{2}}{\text{/H}}^{\text{+}}$

• D

  ${\text{NaOH/NaI/H}}^{\text{+}}$