In the following reaction, what is X?

 ${\mathrm{C}}_2{\mathrm{H}}_2\underset{{\mathrm{HgSO}}_4,{\mathrm{H}}_2{\mathrm{SO}}_4}{\overset{{\mathrm{H}}_2\mathrm{O},60°\mathrm{C}}{\to }}\mathrm{X}\iff {\mathrm{CH}}_3\mathrm{CHO}$

Hg catalyst is used for terminal alkyne hydration. This reaction adds an OH with Markovnikov regioselectivity to form an enol. The enol product then tautomerizes to form a ketone. This can be explain with the help of reaction ${\mathrm{C}}_2{\mathrm{H}}_2\underset{{\mathrm{HgSO}}_4,{\mathrm{H}}_2{\mathrm{SO}}_4}{\overset{{\mathrm{H}}_2\mathrm{O},60°\mathrm{C}}{\to }} {\mathrm{H}}_2\mathrm{C}=\mathrm{CHOH}\iff {\mathrm{CH}}_3\mathrm{CHO}$ 

Hence , the correct option (D) .$H_{2}C = CHOH$