What is the chemical formula of phosphoric acid? A. HPO4 B. H3PO4 C. H3PO3 D. H2PO4

The correct answer is $\boxed{\text{B. }H_3PO_4}$. Phosphoric acid is a weak acid with the molecular formula $\ce{H3PO4}$. It is a colorless, odorless, and syrupy liquid that is used in a variety of applications, including food additives, fertilizers, and detergents.

Option A, $\ce{HPO4}$, is the chemical formula of monohydrogen phosphate. Option C, $\ce{H3PO3}$, is the chemical formula of phosphorous acid. Option D, $\ce{H2PO4}$, is the chemical formula of dihydrogen phosphate.