c
Disequatorial cis \(-1,\,3-\) Dimethylcyclohexane is more stable as both methyl groups are equatorial and are away from each other. (Refer to Image \(I\))

It is followed by trans \(-1,\,3-\) Dimethylcyclohexane where one \(-C H_{3}\) group is equatorial and other is axial (Refer to Image \(II\))

Diaxial cis \(-1,\,3-\) Dimethylcyclohexane is less stable due to large amount of steric strain due to the interaction of axial - \(\mathrm{CH}_{3}\) groups. (Refer to Image \(III\) )

\((I) > (II) \approx (III) > (IV)\)