According to the Br�nsted-Lowry definition, which of the following is formed when a base dissociates in water?

The answer is a conjugate acid. According to the BL definition, acids and bases must come in what is called "conjugate" pairs. For example, if an acid dissociates in water, it will donate a proton to a "conjugate base," and if a base dissociates in water, it will accept a proton from a "conjugate acid."