**Core Concept**
The combination of diuretics with ACE inhibitors is a common strategy in managing hypertension and heart failure, aiming to reduce blood pressure and fluid overload while minimizing electrolyte imbalances.

**Why the Correct Answer is Right**
The correct diuretic to combine with ACE inhibitors is a potassium-sparing diuretic, such as **spironolactone**. When ACE inhibitors are used, they can increase bradykinin levels, leading to vasodilation and a decrease in aldosterone levels. However, aldosterone suppression can also lead to hyperkalemia. Potassium-sparing diuretics like spironolactone counteract this effect by acting as an aldosterone antagonist, thereby preventing potassium loss and reducing the risk of hyperkalemia.

**Why Each Wrong Option is Incorrect**
**Option A:** Furosemide is a loop diuretic that can cause significant potassium loss, exacerbating hyperkalemia when combined with ACE inhibitors.
**Option B:** Thiazide diuretics can also increase potassium loss, making them a poor choice when combined with ACE inhibitors.
**Option C:** Metolazone is a thiazide-like diuretic that may not provide sufficient potassium-sparing effects to safely combine with ACE inhibitors.

**Clinical Pearl / High-Yield Fact**
When combining diuretics with ACE inhibitors, always consider the potential for hyperkalemia and choose a potassium-sparing diuretic like spironolactone to mitigate this risk.

**Correct Answer:** C.