Identify the reagents $A$ and $B$ respectively in the following reactions. $\mathrm{CH}_3 \mathrm{COOH} \stackrel{A}{\longrightarrow} \mathrm{CH}_3 \mathrm{COCl} \stackrel{B}{\longrightarrow} \mathrm{CH}_3 \mathrm{CHO}$

• Correct answer
  A

  $\mathrm{SOCl}_2, \mathrm{H}_2 / \mathrm{Pd}-\mathrm{BaSO}_4$
• B

  $\mathrm{H}_2 / \mathrm{Pd}-\mathrm{BaSO}_4, \mathrm{SOCl}_2$
• C

  $\mathrm{SOCl}_2, \mathrm{H}_2 \mathrm{O}_2$
• D

  $\mathrm{SOCl}_2, \mathrm{O}_5 \mathrm{O}_4$

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