$HC \equiv CH\mathop {\xrightarrow{{30\%\, {H_2}S{O_4}}}}\limits_{HgS{O_4}} A\xrightarrow{{NaOH}}B$




$[A]\,\,\begin{array}{*{20}{c}} {C{H_3} - C - {O^ - }} \\ {\,\,||} \\ {\,\,O} \end{array}$
$[B]\,\,CH_3O^-$
$[C]\,\,CN^-$
$[D]\,\,$ 
$A\xrightarrow[(ii)\;H_3O^+]{(i)\;CH_3MgBr}B\xrightarrow[573\;K]{Cu}2-$methyl $2-$butene
$A$ માં કાર્બનની દળની ટકાવારી ........ હશે.