This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiac Output, Subject name: Physiology
[{'content': 'Under normal circumstances, left ventricular shoening fraction (LVSF) is: \nSelect and explain. \nA. 20%, B. 40%, C. 60%, D. 75%', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Left ventricular shoening fraction (LVSF) is the percentage of shoening of LV fibers from their end-diastolic length (EDL). EDL and ESL are end-diastolic length and end-systolic length, respectively. Normal LVSF = 35%-40%. The value of LVSF decreases in LV failure.', 'role': 'assistant'}]