$\mathrm{Ph}-\mathrm{C} \equiv \mathrm{C}-\mathrm{CH}_{3} \stackrel{\mathrm{Hg}^{2+} / \mathrm{H}^{+}}{\longrightarrow} \mathrm{A}$

• Correct answer
  A

  
• B

  
• C

  
• D

  

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