Due to ocean acidification, when the ocean becomes more acidic, what happens to the pH level of the ocean?

The correct option is: The pH level goes down.

To understand why this is correct, we can look at what happens chemically during ocean acidification.

Ocean acidification occurs when the ocean absorbs carbon dioxide (CO₂) from the atmosphere. When carbon dioxide dissolves in seawater, it reacts with water (H₂O) to form carbonic acid (H₂CO₃). This carbonic acid then dissociates, releasing hydrogen ions (H⁺) into the water.

The pH scale is a measure of the concentration of these hydrogen ions (H⁺) in a solution. The mathematical relationship between pH and hydrogen ion concentration is defined as:
$$\mathrm{pH}=-{\log }_{10}\left[H^{+}\right]$$
Because of the negative logarithm in this formula, the pH scale has an inverse relationship with the concentration of hydrogen ions. This means that as the concentration of hydrogen ions (H⁺) increases (making the solution more acidic), the pH value decreases.

Therefore, as ocean acidification increases the concentration of hydrogen ions, the pH level of the ocean goes down.