Correct Answer - C
In `S_(N^(2))`
Rate of reaction depends upon the concentration of both substrate and reagent.
Hence order of reaction = 2, and it is biomolecular nucleophilic addition reaction.
`underset("Substrate")(CH_(3))-Cl+aq.underset("Reagent")(KOH) rarr CH_(3)-Cl+K^(+)+Cl^(-)`