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
Ultrasonography of umbilical artery is done to know about : 
Select and explain. 
A. Heart beat, B. Gestational age, C. Fetal weight, D. Fetal maturity
A: Heart beat
Answer: A: Heart beat 
Explanation: Doppler ultrasound is presently most widely employed in the detection of fetal cardiac pulsation and pulsation in the various fetal blood vessels.