Chemistry - Halogen Derivative Question with Solution | TestHub

Conjugate base (nucleophile) is strong if acid is weak and vice-versa.
(B) ${\mathrm{CH}}_3{\mathrm{O}}^{-}$is a conjugate base of ${\mathrm{CH}}_3\mathrm{OH}$ (II). (C) ${\mathrm{CN}}^{-}$is a conjugate base of $\mathrm{HCN}$ (III).
Order of acidic nature is IV $>$ I $>$ III $>$ II. Hence, the decreasing order of nucleophilicity is $\mathrm{B}>\mathrm{C}>\mathrm{A}>\mathrm{D}$.