Assertion: o-Nitrophenol is less soluble in water than the m- and p-isomers.

Reason: m- and p- Nitrophenols exist as associated molecules.

This is a assertion and reason answer type question as classified in NCERT Exemplar

(v) Both assertion and reason are correct statements but reason is not correct explanation  of assertion.

Explanation:  Due to intramolecular hydrogen bonding o-Nitrophenol does not form hydrogen bond with  water