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: Unknown
[{'content': '"a" wave in JVP indicates: \nSelect and explain. \nA. Atrial systole, B. Ventricular systole, C. Atrial relaxation, D. Tricuspid regurgitation', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A wave: Arc positive waves due to distention producedby right atrial contraction Large a waves: Indicate atrium is contracting against increased resistance tricuspid stenosis, pulmonary stenosis, pulmonary hypertension.\nCannon S waves\nRegularly: During junctional rhythm. Irregularly: complete Heart Block. Absent a waves: Atrial Fibrillation', 'role': 'assistant'}]