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
[{'content': 'What is the normal left ventricular ejection fraction? \nSelect and explain. \nA. 20%, B. 30%, C. 50%, D. 65%', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Normal left ventricular ejection fraction ranges from 55% to 70%. It is the measurement of how much blood is pumped out of the left ventricle of the hea in each contraction . It is expressed in percentage. If the EF is below normal value, it can be a sign of hea failure', 'role': 'assistant'}]