**Core Concept**
During severe exercise, the body undergoes a series of physiological changes to meet the increased demand for energy. One of these changes involves the accumulation of lactic acid, leading to a decrease in blood pH. This phenomenon is known as lactic acidosis.

**Why the Correct Answer is Right**
The correct answer is due to the increased production of lactic acid as a result of anaerobic glycolysis. When the body's oxygen supply is insufficient to meet the energy demands of exercising muscles, the cells switch to anaerobic glycolysis, a process that generates energy from glucose without the need for oxygen. However, this process also produces lactic acid as a byproduct, which accumulates in the blood and lowers the pH. The enzyme lactate dehydrogenase (LDH) plays a crucial role in this process by converting pyruvate to lactate.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the physiological changes that occur during severe exercise.

**Option B:** While it is true that the respiratory system plays a role in regulating pH, it is not directly responsible for the decrease in pH during severe exercise.

**Option C:** This option is incorrect because the kidneys primarily regulate pH through the excretion of hydrogen ions, but they are not directly responsible for the decrease in pH during severe exercise.

**Clinical Pearl / High-Yield Fact**
The accumulation of lactic acid during severe exercise can lead to fatigue, muscle cramps, and even respiratory distress. It is essential to recognize the signs and symptoms of lactic acidosis and take prompt action to address the underlying cause.

**Correct Answer:** C. Increased production of lactic acid through anaerobic glycolysis.