This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
A wave in JVP is due to ? 
Select and explain. 
A. Atrial systole, B. Atrial diastole, C. Ventricular systale, D. Ventricular diastole
A: Atrial systole
Answer: A: Atrial systole 
Explanation: Ans. is 'a' i.e., Atrial systole