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: Radiology
[{'content': 'True about umbilical aery Doppler is \nSelect and explain. \nA. Changes in the flow velocity waveforms of umbilical aery may be impoant in the management of high-risk pregnancies, B. Absence of end-diastolic flow is normal at term, C. Maternal smoking decreases SID ratio, D. Increased diastolic flow indicates worse prognosis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Absence of end-diastolic flow is normal at term', 'role': 'assistant'}]