Question

The number of compounds which undergo tautomerism to form an aromatic product are :

Answer 1

Compounds (a), (d) and (f) when undergo tautomerism form compounds which are aromatic as shown :
Compounds (b) and (c) also undergo tautomerism, but they form non-aromatic and anti-aromatic products respectively as shown.

Compound (e) does not have any $s{p}^3$ hybridised carbon having $\alpha$-hydrogen, so it does not undergo tautomerism.

So correct answer is 3