Normally cardiac cycle takes complete:

Correct Answer: D

Rationale: At a normal heart rate of 75 bpm, the cardiac cycle lasts ~0.8 seconds (D, 60/75 = 0.8 s). A, B, and C are too short for a full cycle.

Correct Answer: D

Rationale: The T wave (D) represents ventricular repolarization. P wave (A) is atrial depolarization, QRS (B) is ventricular depolarization, and U wave (C) is minor/uncertain.

Correct Answer: C

Rationale: Resting cardiac output is ~5.25 L/min (C, 70 ml × 75 bpm). A and B are too low, D too high for rest.

Correct Answer: C

Rationale: S₂ (C) has a longer, sharper sound (~0.08 s) than S₁ (~0.07 s) due to semilunar valve closure. A is S₁, B is true but not unique, D is secondary.

Correct Answer: A

Rationale: Coronary arteries (A) supply oxygenated blood to the myocardium. Coronary veins (B) and sinus (C) drain deoxygenated blood, pulmonary artery (D) carries deoxygenated blood to lungs.