$$ \text { Identify the reagent used in following conversion. } $$

• A

  $\mathrm{CO}, \mathrm{HCl} / \mathrm{AlCl}_3$
• B

  $\mathrm{CrO}_2 \mathrm{Cl}_2 \cdot \mathrm{H}_3 \mathrm{O}^{+}$
• Correct answer
  C

  $\mathrm{AlH}(\mathrm{i}-\mathrm{Bu})_2, \mathrm{H}_3 \mathrm{O}^{+}$
• D

  $\mathrm{CrO}_3,\left(\mathrm{CH}_3 \mathrm{CO}\right)_2 \mathrm{O}$

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