KEAM 2018 Physics and Chemistry Paper

(a) Structure (a) has two π -bonds and one lone pair of electrons over N -atom and has planer structure. Thus, is an aromatic compound.
Thus, is an aromatic compound.(b) The structure (b) also contain two π -bonds and one lone pair of electrons. Thus, follow Huckel's rule. The structure is cyclic and planer.
∴(b) is also an aromatic compound.(c) The structure (c) has only 2‌pi -bonds and do not follow Huckel's rule. So, it not an aromatic compound.(d) Structure (d) also contain only two π -bonds, thus do not follow Huckel's rule and is not an aromatic compound.
∴(a) is the correct answer.