Q.Identify giving reason whether the following compounds are aromatic or not.
A. B. C. D. (structures as printed in the textbook)

Aromaticity, formalised by Huckel's rule, is the property responsible for benzene's -- and every aromatic compound's -- unusual stability and preference for substitution over addition, arising from extensive cyclic delocalisation of pi electrons in a planar ring. Three conditions together define an aromatic compound: it must be cyclic and planar, with every ring atom sp2-hybridised (hence bearing an available p-orbital); every ring atom's p-orbital must be parallel to its neighbours so continuous overlap is possible all the way around; and, only once these structural conditions are met, the resulting cyclic pi system must contain (4n+2) pi electrons for some whole number n. Benzene (6 pi electrons, n=1), naphthalene (10 pi electrons, n=2), and pyridine (6 pi electrons in the ring system, with nitrogen's lone pair sitting separately) a …