**Core Concept**
Acetazolamide is a carbonic anhydrase inhibitor used in the treatment of glaucoma, epilepsy, and altitude sickness. It works by inhibiting the enzyme carbonic anhydrase, which is involved in the regulation of bicarbonate and hydrogen ion concentrations in various tissues.

**Why the Correct Answer is Right**
Acetazolamide inhibits carbonic anhydrase in the ciliary body of the eye, leading to a decrease in aqueous humor production and a subsequent reduction in intraocular pressure. It also crosses the blood-brain barrier and inhibits carbonic anhydrase in the brain, which helps to reduce seizures in patients with epilepsy. Additionally, acetazolamide can induce diuresis and increase respiratory alkalosis by inhibiting carbonic anhydrase in the kidneys and lungs, respectively.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because acetazolamide is not a direct vasodilator, unlike other medications used to treat altitude sickness.
**Option B:** This option is incorrect because acetazolamide is not primarily used as an antihypertensive agent, although it may have a mild diuretic effect.
**Option C:** This option is incorrect because acetazolamide is not a direct adrenergic agonist, unlike other medications used to treat glaucoma.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that acetazolamide can cause a rebound increase in intraocular pressure if stopped abruptly in patients with glaucoma, so gradual tapering of the medication is necessary to avoid this complication.

**Correct Answer: C. Diuretic and carbonic anhydrase inhibitor.**