The correct order of acid strength of benzoic acid (I), 4-methylbenzoic acid (II) and 4-nitrobenzoic acid (III) is

AIII > I > II
BI > III > II
CII > I > III
DI > II > III

Answer: A

The 4-methyl group donates electrons by +I and hyperconjugation, destabilising the carboxylate and weakening the acid. The 4-nitro group withdraws electrons by -M and -I, stabilising the carboxylate. So 4-nitro > benzoic > 4-methyl.

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