Answer : The correct option is, The pH decreases.
Explanation :
As we know that,
pH : It is defined as the negative logarithm of hydrogen ion concentration.
Mathematically it is represented as :
![pH=-\log [H^+]](https://img.qammunity.org/2019/formulas/physics/high-school/iidawris7irvi0bu33z0a9xjzagtaknk6o.png)
According to the question, when the concentration of hydrogen ion increases then the value of pH decreases and the acidity of the solution also increases that means the solution is more acidic in nature.
Hence, if the hydrogen ion concentration increases, the pH decreases.