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
[{'content': "The left atrial yvas lay than 'a' wave in comparison to right atrium because: \nSelect and explain. \nA. Left side is high pressure system, B. Left atrium is more compliant, C. Left atrium is compressed posteriorly by pulmonary veins, D. Right atrial pressure is transmitted into the pulmonary circulation", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. a. Left side is high pressure system', 'role': 'assistant'}]