Arrange the following anions in decreasing leaving ability in ${\mathrm{S}}_{\mathrm{N}}2$ reaction -

$\mathrm{I}.{ \mathrm{CF}}_3{\mathrm{CO}}_2^{\mathrm{ }-}$

$\mathrm{II}.{ \mathrm{CH}}_3{\mathrm{SO}}_3^{-}$

$\mathrm{III}. {\mathrm{CF}}_3{\mathrm{SO}}_3^{-}$

$\mathrm{IV}. \mathrm{p}-\mathrm{nitrobenzenesulphonate}$

Given below are two statements :

Statement I : ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}$ and $\mathrm{AgCN}$ both can generate nucleophile.

Statement II : $\mathrm{KCN}$ and $\mathrm{AgCN}$ both will generate nitrile nucleophile with all reaction conditions.

Choose the most appropriate option :

The correct statement regarding electrophiles is:

Which of the following statements is not correct for a nucleophile?

${\mathrm{CH}}_3-\stackrel{⊝}{\mathrm{S}}\stackrel{\oplus }{\mathrm{Na}}+{\mathrm{CH}}_3-{\mathrm{CH}}_2-\mathrm{x}⟶$

The reaction is fastest when $\mathrm{X}$ is