Which of the following classes of medication decreases heart rate, contractility, and blood pressure, and is used to increase survival rates in post-myocardial infarction patients?

The correct answer is C: Beta blockers. Beta blockers decrease heart rate and contractility by blocking the effects of catecholamines on beta receptors, leading to reduced blood pressure. In post-myocardial infarction patients, beta blockers improve survival rates by reducing myocardial oxygen demand and protecting against arrhythmias. ACE inhibitors (A) primarily reduce blood pressure by inhibiting the renin-angiotensin-aldosterone system. Vasodilators (B) directly dilate blood vessels to lower blood pressure but do not affect heart rate or contractility. Diuretics (D) promote fluid excretion to reduce blood volume and pressure, but do not specifically target heart rate or contractility.