The reaction of bromobenzyl chloride with NaCN in ethanol leads to the formation of 

4-bromobenzyl cyanide

The correct answer is option 4. 4-bromobenzyl cyanide.

The reaction of bromobenzyl chloride with \(NaCN\) in ethanol is a nucleophilic substitution reaction. The cyanide ion \((CN^-)\) attacks the carbon atom that is bonded to the bromine atom, displacing the bromine atom. The product of the reaction is 4-bromobenzyl cyanide.

The other options are incorrect. Option (1) 4-bromo-2-cyanobenzyl chloride, is not formed because the cyanide ion attacks the carbon atom that is bonded to the bromine atom, not the carbon atom that is bonded to the chlorine atom. Option (2) 4-cyanobenzyl cyanide, is not formed because the cyanide ion cannot form two bonds to the same carbon atom. Option (3) 4-cyanobenzyl chloride, is not formed because the chloride ion is a poor leaving group.