The correct statement about the reaction is:
HCl is an acid, and Cl– is its conjugate base.
In the reaction, HCl donates a proton (H+) to water (H2O), forming H3O+ and Cl–. HCl, as the acid, loses a proton and forms the conjugate base Cl–. Therefore, this option accurately describes the role of HCl and Cl– in the reaction.