The reagent used for converting acetylene to oxalic acid is

• A

  $\mathrm{HgSO}_4$ /aqueous $\mathrm{H}_2 \mathrm{SO}_4$
• B

  $\mathrm{HgSO} / \mathrm{CH}_{\mathrm{O}} \mathrm{COOH}$
• Correct answer
  C

  $\mathrm{KMnO}_4 / \mathrm{KOH}, 25^{\circ} \mathrm{C}$
• D

  $\mathrm{Cr}_2 \mathrm{O}_3 / \mathrm{H}_2 \mathrm{SO}_4$

Hence, the correct answer is option: 'C'.