${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{I} + \mathrm{KOH}\left(\mathrm{aq}\right) \to {\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH} + \mathrm{KI}$

The above reaction is an example of -

1. Nucleophilic substitution reaction

2. Elimination reaction

3. Addition reaction

4. Electrophilic substitution reaction

Elimination reaction among the following is-