This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Anatomy
Engagement of fetal head is with reference to 
Select and explain. 
A. Biparietal diameter, B. Bitemporal diameter, C. Occipitofrontal diameter, D. Suboccipitofrontal diameter
A: Biparietal diameter
Answer: A: Biparietal diameter 
Explanation: Engagement is said to occur when the largest transverse diameter of fetal head crosses the pelvic inlet. Largest transverse diameter of fetal head is biparietal diameter