Which one of the following gives the highest amount of hydrogen ions (H"^) ?

The concentration of hydrogen ions (H+) is inversely proportional to the pH value of a substance. Gastric juice, which contains hydrochloric acid (HCl), is a strong mineral acid that dissociates almost completely in water. It typically has a very low pH, often around 1 to 2, indicating a high concentration of H+ ions. In contrast, lemon juice (citric acid) is a weaker acid with a higher pH (around 2.2 to 3). Sodium hydroxide is a strong base with a high pH (near 14), and milk of magnesia is a weak base with a pH of approximately 10.5. Scientific data indicates that the concentration of H+ ions in the stomach (gastric juice) is significantly higher—up to a billion times more—than in antacids like milk of magnesia. Therefore, gastric juice provides the highest amount of hydrogen ions among the given options.