In a reaction having both alkyl halide and base, the base will attack on:

Explanation

The base attacks the beta hydrogen atom instead of the carbon atom that is attached to the halogen. This is known as an elimination reaction, and it occurs when the base is strong enough to abstract a proton from the beta carbon atom, resulting in the formation of a double bond between the alpha and beta carbon atoms and the elimination of the halide ion. This reaction is known as the E2 mechanism. The selectivity between nucleophilic attack and elimination depends on the nature of the base, the structure of the alkyl halide, and the reaction conditions.