**Core Concept:** Metabolic alkalosis is a condition characterized by an increase in blood pH due to elevated levels of bicarbonate ions (HCO3-). It can be caused by various factors, including increased bicarbonate excretion, decreased bicarbonate reabsorption, and decreased chloride excretion.

**Why the Correct Answer is Right:** Option D, Diuretic therapy, leads to increased bicarbonate excretion in the kidneys, contributing to the development of hyperventilation and thus, increased HCO3- in the blood.

**Why Each Wrong Option is Incorrect:**

A. **Increased Cl(-) excretion (Option A):** This is incorrect because increased chloride excretion would result in hypokalemia, not alkalosis. It typically occurs in conditions like cirrhosis or hypochloremic alkalosis.

B. **Decreased HCO3- reabsorption (Option B):** This is incorrect because decreased bicarbonate reabsorption would lead to hypocapnia, causing a decrease in blood pH, not alkalosis. It often occurs in renal tubular acidosis or Bartter's syndrome.

C. **Increased HCO3- production (Option C):** This is incorrect because increased bicarbonate production would lead to a decrease in blood pH, not alkalosis. It is seen in carbonic anhydrase inhibitors, like acetazolamide, or in conditions like respiratory alkalosis.

**Clinical Pearl:** Metabolic alkalosis should be differentiated from respiratory alkalosis, which is caused by a decrease in PCO2, leading to a decrease in pH, not an increase in pH as seen in alkalosis. Understanding this distinction is crucial for accurate diagnosis and management of patients with altered acid-base balance.

**Correct Answer:** D. Diuretic therapy, as it increases bicarbonate excretion, leading to alkalosis.