Explain why adding a base to pure water causes the concentration of hydronium ions (H₃O⁺) to decrease.

• A. The base reacts with H₃O⁺, forming its conjugate acid; thus, reducing the concentration of acidic H₃O⁺ ions.
• B. The base reacts with water to form H₃O⁺ ions; thus, reducing the concentration of H₃O⁺ ions.
• C. The base reacts with the hydroxide ions (OH⁻) to form more water molecules.
• D. The base has a higher affinity for hydrogen ions (H⁺) than water molecules, leading to a decrease in the concentration of hydronium ions (H₃O⁺).

Answer: (A)