**Core Concept**
Potassium-sparing diuretics are a class of medications that help the kidneys eliminate excess fluid from the body while minimizing potassium loss. This is particularly beneficial for patients with conditions like heart failure, hypertension, or kidney disease, where potassium levels may be low.

**Why the Correct Answer is Right**
The correct answer is a potassium-sparing diuretic that works by inhibiting the sodium-potassium ATPase (Na+/K+ ATPase) pump in the collecting duct of the kidneys. This pump is responsible for reabsorbing sodium ions from the filtrate and secreting potassium ions into the filtrate. By blocking this pump, the correct answer reduces sodium reabsorption and increases potassium reabsorption, thereby sparing potassium in the body.

**Why Each Wrong Option is Incorrect**
* **Option A:** This is a loop diuretic that acts on the thick ascending limb of the loop of Henle to inhibit sodium, potassium, and chloride reabsorption. It does not spare potassium.
* **Option B:** This is a thiazide diuretic that acts on the distal convoluted tubule to inhibit sodium and chloride reabsorption. It increases potassium excretion and does not spare potassium.
* **Option C:** This is a carbonic anhydrase inhibitor that acts on the proximal convoluted tubule to inhibit sodium and bicarbonate reabsorption. It increases potassium excretion and does not spare potassium.

**Clinical Pearl / High-Yield Fact**
When using potassium-sparing diuretics, it's essential to monitor potassium levels regularly, especially in patients with underlying kidney disease or heart failure, as they can be at risk of hyperkalemia.

**Correct Answer: C. Amiloride**