The concept of resonance explains various properties of compounds.The molecule with conjugated system of `pi` bonds, are stabilized by resonance and have low heat of hydrogenation .Hyperconjugative stabilization also decreases heat of hydrogenation. In aromatic rings a functional group with a lone pair of electron exerts +m effect.Some functional groups like -NO, -NC, `-CH=CH_2` can function both as electrons releasing (+m,+R) or electron withdrawing (-m,-R) groups.More extended conjugation provides more stabilization.
The most stable resonating structure of following compound is
A.
B.
C.
D.
