b
$(b)$ $\begin{matrix}
\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,O \\
\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|| \\
HC\equiv CH\xrightarrow[{{H}_{2}}S{{O}_{4}}]{HgS{{O}_{4}}}C{{H}_{3}}-CH\xrightarrow[{{H}^{\oplus }}]{N{{H}_{3}}+HCN} \\
\end{matrix}\begin{matrix}
N{{H}_{3}}\,\,\,\, \\
|\,\,\,\,\,\,\,\,\,\, \\
C{{H}_{3}}-CH-COOH \\
\end{matrix}$