This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
S3 is due to 
Select and explain. 
A. Rapid gushing of blood into ventricle, B. Atrial contraction, C. AV valve closure, D. Semilunar valve closure
A: Rapid gushing of blood into ventricle
Answer: A: Rapid gushing of blood into ventricle 
Explanation: S3 is due to the rapid gush of blood in the ventricle Ref: Ganong 25th ed/page 540