Which one of the following is a tribasic acid?

The basicity of an acid is defined by the number of replaceable hydrogen ions (protons) it can donate per molecule in an aqueous solution. Hydrochloric acid (HCl) and nitric acid (HNO3) are classified as monobasic or monoprotic acids because they dissociate to produce only one H+ ion. Sulphuric acid (H2SO4) is a dibasic or diprotic acid as it contains two ionizable hydrogen atoms. Phosphoric acid (H3PO4) is a tribasic (triprotic) acid because it possesses three acidic hydrogen atoms that can be donated during dissociation. While the strength of an acid depends on its degree of ionization, basicity specifically refers to the proton count. Therefore, phosphoric acid is the correct example of a tribasic acid among the given options.