Answer:
correct option is (b) (4n+2)π electrons
Explanation:
The compound represented by option (B) is not aromatic.
Cyclooctatetraene prefers to adopt a more stable non-planar conformation.
Note: For a molecule to be aromatic, it should have planar, cyclic, conjugated system of (4n+2)π electrons.
Rest all are planar and follows Huckel rule. Thus they are aromatic.
Cyclooctatetraene is nonaromatic in nature as it does not follow Huckel's rule of aromaticity
In the case of option D lone pair of the nitrogen is in conjugation with double bond, on resonance forms cyclopentadienyl anion which is an aromatic compound.
Hence option B is the correct answer.