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
Most accurate assessment of gestational age by USG is done by – 
Select and explain. 
A. Femur length, B. Gestational sac size, C. Menstrual history, D. Crown rump length
D: Crown rump length
Answer: D: Crown rump length 
Explanation: None