Final answer:
The lower the pH, the higher the concentration of H₃0⁺ ions.
Step-by-step explanation:
The lower the pH, the higher the concentration of H₃0⁺ ions.
A solution with a pH lower than 7 is called an acid, and as the hydronium ion concentration increases in the solution, the pH value decreases. Therefore, the more acidic a solution is, the lower its pH value is. For example, a solution with a pH of 1 is more acidic and has a higher concentration of H₃0⁺ ions compared to a solution with a pH of 4.
So, the correct answer is higher.