Energetic stability in relation to α-hydrogens
Apparently the intent of the question is to assess the stability of the three alkenes. Evaluation of the heats of formations provides useful information. The NIST site provides heats of formation and hydrogenation all of which are shown in black in the diagram. Computed values appear in red. Because hydrogenation of A, B and C all provide ethylcyclopentane, the greater the heat of hydrogenation the less stable the alkene. Alternatively, the less negative the heat of formation, the less stable. Thus, the order of stability is A &lt; C &lt; B.