Organic Chemistry – Some Basic Principles Part 2

(A) In o-nitrophenol intramolecular hydrogen bonding takes place.
(B) Extensive H-bonding is observed in this case as two H-atoms bonded to strongly electronegative atoms (nitrogen, oxygen) are present. H-bonding occurs when H-bonded to strongly electronegative atoms exists in the vicinity of other electronegative atoms possessing lone pairs of electron.
(C) Here, only one hydrogen atom bonded to electronegative oxygen atom is present. So, intermolecular H-bonding is present but not so extensive.
So, option (a) is correct.