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
Under normal circumstances, left ventricular shoening fraction (LVSF) is: 
Select and explain. 
A. 20%, B. 40%, C. 60%, D. 75%
B: 40%
Answer: B: 40% 
Explanation: 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.