At room temperature, disproportionation of an aqueous solution of in situ generated nitrous acid $\left(\mathrm{HNO}_2\right)$ gives the species

• Correct answer
  A

  $\mathrm{H}_3 \mathrm{O}^{+}, \mathrm{NO}_3^{-}$and $\mathrm{NO}$
• B

  $\mathrm{H}_3 \mathrm{O}^{+}, \mathrm{NO}_3{ }^{-}$and $\mathrm{NO}_2$
• C

  $\mathrm{H}_3 \mathrm{O}^{+}, \mathrm{NO}^{-}$and $\mathrm{NO}_2$
• D

  $\mathrm{H}_3 \mathrm{O}^{+}, \mathrm{NO}_3{ }^{-}$and $\mathrm{N}_2 \mathrm{O}$

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