The correct order of basic strength of piperidine (I), pyridine (II) and pyrrole (III) in water is

AII > I > III
BIII > II > I
CI > II > III
DI > III > II

Answer: C

Piperidine has a localised sp3 nitrogen lone pair and is the strongest base. Pyridine's lone pair is sp2 in the plane and free to bind H+, though held more tightly than an sp3 lone pair. In pyrrole the lone pair is part of the aromatic sextet, so protonation would destroy aromaticity and pyrrole is by far the weakest base.

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