b
\(\underset{\text { (wA) }}{ C _6 H _5 COOH }+\underset{\text { (SB) }}{ NaOH } \longrightarrow \underset{\text { (Salt) }}{ C _6 H _5 COONa }+ H _2 O\)

\(( A ) \rightarrow( B )\) Free \(H ^{+}\)ions are replaced by \(Na ^{\oplus}\) which decreases conductance.

\((B) \rightarrow (C)\) Un-dissociated benzoic acid reacts with \(NaOH\) and forms salt which increases ions \ conductance increases.

\((C) \rightarrow (D)\) After equivalence point at (3), \(NaOH\) added further increases \(Na ^{\oplus}\) and \(OH ^{\circ}\) ions which further increases the conductance.