Which of the following compounds is aromatic in nature?

Step-by-step solution

In (a), due to the presence of (4 n+2) e⁻ it follows Huckel's rule and therefore, it is aromatic. In (b), due to the presence of extra lone pair of electrons, total e⁻ comes out to be 4 e⁻ . Thus, it is anti-aromatic. In (c), although it is cyclic and has conjugated 8 e⁻ but Huckel's (4 n+2) rule is not followed and also ring is not planar. Hence, it is nonaromatic. In ( d ) , it has 6 e⁻ in conjugation but not in the ring, hence it is non-aromatic.