Benzene is more stable than hypothetical cyclohexatriene due to the delocalization of electrons in the π electron cloud of the aromatic ring. This delocalization of electrons leads to a more stable electronic configuration in benzene, as the electrons are shared more evenly between all six carbon atoms in the ring. This is in agreement with Assertion A.

Reason R is also correct, as the delocalized π electron cloud in the aromatic ring is attracted more strongly by the nuclei of the carbon atoms. This is due to the fact that the π electrons in the ring are more spread out and are not localized to a single atom, which makes them more attracted to the positively charged nuclei of the carbon atoms. This explanation supports Assertion A.