The correct statement about the reaction is:
HCl is an acid, and Cl– is its conjugate base.
In this reaction, HCl donates a proton (H+) to water (H2O), resulting in the formation of Cl– (the conjugate base of HCl) and H3O+ (the hydronium ion, which is the conjugate acid of water). Therefore, HCl is the acid, and Cl– is indeed its conjugate base.