**Core Concept**
ACE inhibitors are a class of medications that block the action of angiotensin-converting enzyme (ACE), a naturally occurring substance in the body that constricts blood vessels and increases blood pressure. By inhibiting ACE, these drugs relax blood vessels, reduce blood pressure, and decrease the heart's workload.

**Why the Correct Answer is Right**
The correct answer is an ACE inhibitor because it blocks the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor. This results in decreased peripheral resistance, reduced blood pressure, and decreased aldosterone levels. ACE inhibitors also increase the levels of bradykinin, a vasodilator, which further contributes to their hypotensive effects.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while it may have some effects on blood pressure, it is not an ACE inhibitor. **Option B:** This option is incorrect because it is actually a beta-blocker, which works by blocking the effects of the sympathetic nervous system on the heart. **Option C:** This option is incorrect because it is an alpha-blocker, which works by blocking the effects of the sympathetic nervous system on blood vessels.

**Clinical Pearl / High-Yield Fact**
ACE inhibitors are often used in patients with heart failure, hypertension, and diabetic nephropathy. They are also used to protect the kidneys in patients with chronic kidney disease.

**Correct Answer:** C. Lisinopril.