${\text{C}}_{\text{2}}{\text{H}}_{\text{2}}\underset{{\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}}{\overset{\text{1\%}{\text{Hg}}_{\text{2}}{\text{(OH)}}_{\text{2}}}{\to }}\text{A}\stackrel{\text{[O]}}{\to }\text{B,}$ , B is

• Correct answer
  A

  An acid
• B

  An aldehyde
• C

  A ketone
• D

  Ethanol

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