- A Valves present within the vena cava
- B Semilunar valves at the start of diastole
- C Tricuspid and bicuspid (atrioventricular) valves
- D Walls of the pulmonary artery during systole
Correct answer: C. Tricuspid and bicuspid (atrioventricular) valves
Explanation: The first heart sound (lub) results from the closure of the atrioventricular valves (tricuspid and bicuspid) at the start of ventricular systole.
Concept context
Blood, lymph, the heart, the cardiac cycle, blood pressure, and ECG. High NEET weightage.