Which statement best defines an Arrhenius acid?

• A. A substance that donates an electron pair to form a coordinate covalent bond
• B. A substance that increases the concentration of $O^{2^{-}}$ in the gas phase
• C. A substance that increases the concentration of $H^{+}$ in aqueous solution
• D. A substance that increases the concentration of $O^{2^{-}}$ in aqueous solution

Answer: (C)