When $X{O}_2$ is fused with an alkali metal hydroxide in presence of an oxidizing agent such as ${\mathrm{KNO}}_3$; a dark green product is formed which disproportionate in acidic solution to afford a dark purple solution. $X$ is:

• Correct answer
  A

  $Mn$
• B

  $Cr$
• C

  $V$
• D

  $Ti$

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