**Core Concept**
Pyloric stenosis leads to gastric outlet obstruction, resulting in prolonged vomiting, which causes a metabolic disturbance characterized by electrolyte imbalances and dehydration. The loss of gastric contents, including hydrochloric acid, leads to a compensatory increase in renal hydrogen ion excretion, causing metabolic alkalosis.

**Why the Correct Answer is Right**
The prolonged vomiting causes loss of hydrochloric acid (HCl) and hydrogen ions (H+), leading to a compensatory increase in renal hydrogen ion excretion. This results in a metabolic alkalosis, characterized by an elevated blood pH (alkalosis) and a decreased hydrogen ion concentration. The kidneys increase sodium reabsorption and potassium excretion to compensate for the loss of hydrogen ions. The elevated aldosterone levels also contribute to potassium excretion and sodium retention.

**Why Each Wrong Option is Incorrect**
**Option A:** Metabolic acidosis is incorrect because the loss of hydrochloric acid and hydrogen ions leads to a compensatory increase in renal hydrogen ion excretion, resulting in metabolic alkalosis.
**Option B:** Respiratory acidosis is incorrect because the primary disturbance is metabolic, not respiratory. The patient's respiratory status is not directly related to the metabolic disturbance.
**Option C:** Respiratory alkalosis is incorrect because the primary disturbance is metabolic, not respiratory. The patient's respiratory status is not directly related to the metabolic disturbance.

**Clinical Pearl / High-Yield Fact**
In cases of prolonged vomiting, remember that the kidneys will compensate for the loss of hydrogen ions by increasing renal hydrogen ion excretion, leading to metabolic alkalosis. This can be remembered using the mnemonic "VOMIT" - Vomiting leads to METabolic Alkalosis, Increased aldosterone, and Thirst.

**Correct Answer: C. Respiratory alkalosis is incorrect because the primary disturbance is metabolic, not respiratory. The patient's respiratory status is not directly related to the metabolic disturbance.