**Core Concept**
The question is testing the understanding of the pathophysiology of acid-base balance and the concept of metabolic acidosis. Metabolic acidosis is characterized by an increase in the levels of hydrogen ions in the blood, leading to a decrease in blood pH.

**Why the Correct Answer is Right**
Metabolic acidosis occurs when there is an accumulation of acidic substances in the body, such as lactic acid, or when the kidneys are unable to excrete excess hydrogen ions. This can be due to various reasons, including diabetic ketoacidosis, lactic acidosis, or renal failure. In diabetic ketoacidosis, the body produces excess ketones, which are acidic in nature and contribute to the development of metabolic acidosis.

**Why Each Wrong Option is Incorrect**
**Option A:** This statement is true as metabolic acidosis is often associated with an increase in anion gap, which is calculated by subtracting the chloride concentration from the sodium concentration.

**Option B:** This statement is true as metabolic acidosis can be caused by an increase in the levels of acidic substances, such as lactic acid, in the body.

**Option C:** This statement is false as metabolic alkalosis is characterized by a decrease in the levels of hydrogen ions in the blood, leading to an increase in blood pH.

**Clinical Pearl / High-Yield Fact**
The anion gap is a useful tool in differentiating between metabolic acidosis and metabolic alkalosis. An increased anion gap is typically seen in metabolic acidosis, while a decreased anion gap is seen in metabolic alkalosis.

**Correct Answer:** C. Metabolic alkalosis is characterized by a decrease in the levels of hydrogen ions in the blood, leading to an increase in blood pH.