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: Gynaecology & Obstetrics
[{'content': 'All of the following are commonly used for estimation of gestational age in mid trimester EXCEPT: March 2013 \nSelect and explain. \nA. Biparietal diameter, B. Crown Rump Length, C. Abdominal circumference of fetus, D. Femur length', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B i.e. Crown Rump Length CRL is most accurate with an error of 2.1 days in the first trimester BPD, FL, HC (head circumference) & AC is commonly used for dating thereafter.', 'role': 'assistant'}]