**Core Concept**
Losartan is an angiotensin II receptor antagonist (ARB) used in the management of hypertension and certain types of heart failure. It works by blocking the action of angiotensin II at the receptor level, thereby reducing vasoconstriction and blood pressure.

**Why the Correct Answer is Right**
Losartan selectively blocks the angiotensin II type 1 (AT1) receptor, which is a G-protein-coupled receptor responsible for vasoconstriction and aldosterone secretion. By blocking this receptor, losartan prevents the vasoconstrictive effects of angiotensin II and reduces blood pressure. Losartan also lacks significant affinity for the angiotensin II type 2 (AT2) receptor, which is involved in vasodilation and natriuresis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not accurately describe the mechanism of action of losartan.
**Option B:** This option is incorrect as losartan is not a direct vasodilator, but rather a receptor antagonist.
**Option C:** This option is incorrect as losartan is not a beta-blocker, but rather an ARB.

**Clinical Pearl / High-Yield Fact**
Losartan is a useful alternative to ACE inhibitors in patients with hypertension or heart failure who have contraindications to ACE inhibitors, such as renal artery stenosis or hyperkalemia.

**Correct Answer:** C.