On adding $\mathrm{K}\mathrm{M}\mathrm{n}{\mathrm{O}}_4$ to cold conc. ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ , it gives

• A

  $\mathrm{M}\mathrm{n}{\mathrm{O}}_2$
• B

  $\mathrm{M}{\mathrm{n}}_2{\mathrm{O}}_3$
• Correct answer
  C

  $\mathrm{M}{\mathrm{n}}_2{\mathrm{O}}_7$
• D

  $\mathrm{M}\mathrm{n}{\mathrm{O}}_3$

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