Correct Answer: A

Rationale: Metoprolol is a cardioselective beta-1 adrenergic receptor blocker. It reduces heart rate, myocardial contractility, and cardiac output, leading to decreased blood pressure. In this case, the reduction in blood pressure after administration confirms its beta-blocker activity. Unlike calcium channel blockers that act on vascular smooth muscles, ACE inhibitors that affect the renin-angiotensin system, or direct vasodilators that relax arteriolar smooth muscle, Metoprolol’s primary mechanism is sympathetic inhibition through beta-1 receptor blockade. This drug is widely used in hypertension, angina, and heart failure for its ability to stabilize cardiac workload and oxygen demand.

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