**Core Concept**
Minoxidil is a **potent vasodilator** used in the treatment of severe hypertension and alopecia. It works by directly relaxing smooth muscle in arterioles, causing a decrease in blood pressure.

**Why the Correct Answer is Right**
Minoxidil's mechanism of action involves opening **ATP-sensitive potassium channels** in smooth muscle cells, leading to hyperpolarization and subsequent relaxation. This results in decreased peripheral resistance and lowered blood pressure. Additionally, minoxidil is known for its use in treating alopecia, particularly androgenetic alopecia, by promoting hair growth.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect as the primary action of minoxidil is not as a diuretic.
**Option B:** Incorrect because minoxidil does not act by stimulating the baroreceptors.
**Option C:** Incorrect as minoxidil does not primarily work through the sympathetic nervous system.

**Clinical Pearl / High-Yield Fact**
Minoxidil is notable for its side effects, including **hirsutism** and **pericardial effusion** in some patients, which are important to recognize in clinical practice.

**Correct Answer:** D. It is used in alopecia and causes hirsutism as a side effect.