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': 'Ultrasonography of umbilical artery is done to know about : \nSelect and explain. \nA. Heart beat, B. Gestational age, C. Fetal weight, D. Fetal maturity', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Doppler ultrasound is presently most widely employed in the detection of fetal cardiac pulsation and pulsation in the various fetal blood vessels.', 'role': 'assistant'}]