Which of the following systems are aromatic?

Options

A.
B.
C.
D.

Answer

C, D

Explanation

Although (a) has 10 conjugated pi electrons it is non-aromatic due to lack of planarity of the ring as

(b) has 16(4n) pi-electrons, hence antiaromatic. (c) (azulene) and (d) are aromatic system as they satisfy Huckel rule.