The correct statement regarding nucleophilic substitution reaction in a chiral alkyl halide is ;
Retention occurs in $S_N 1$ reaction and inversion occurs in $\mathrm{S}_{\mathrm{N}} 2$ reaction.
Racemisation occurs in $\mathrm{S}_{\mathrm{N}} 1$ reaction and retention occurs in $\mathrm{S}_{\mathrm{N}} 2$ reaction.
Racemisation occurs in both $\mathrm{S}_{\mathrm{N}} 1$ and $\mathrm{S}_{\mathrm{N}} 2$ reactions.
Racemisation occurs in $S_N 1$ reaction and inversion occurs in $\mathrm{S}_{\mathrm{N}} 2$ reaction.
