(\(d\))is most stable and compound (\(a\)) is least stable among these in compound (\(b\)) and (\(c\)) carbon atom of that positive charge is \(\mathrm{sp}^3\) hybridised they on the basis of angle strain theory compound (\(c\)) is more stable than compound (\(b\)).
$(x)\begin{array}{*{20}{c}}
{O\,\,\,}\\
{||\,\,\,}\\
{C{H_3} - S - O - H}\\
{||\,\,\,\,}\\
{O\,\,\,\,}
\end{array}$
$\begin{array}{*{20}{c}}
{\,\,\,\,\,O}\\
{\,\,\,\,\,\,||}\\
{(y)\,\,\,C{H_3} - C - O - H}
\end{array}$
$(z)\,\, CH_3 -OH$
(1) $CH_2=CH_2$
(2) $[Figure]$
(3) $H-C \equiv C-H$
(4) $NH_3$