Which of the following reaction is correct ?
All of these
Nature of C-X bond -
Carbon atom bear partial positive charge and halogen atom bear a negative charge.
- wherein

SN2 Substitution Nucleophilic bimolecular -
These reactions proceed in only one step, resulting in inversion of the configuration of the attacked carbon atom.
- wherein

All of these are correct.
Therefore, Option(4) is correct