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