This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fetal Skull and Maternal Pelvis, Subject name: Gynaecology & Obstetrics
In a vertex presentation the diameter of engagement is: 
Select and explain. 
A. Suboccipitobregmatic, B. Suboccipito-frontal, C. Occipitofrontal, D. Bitemporal
A: Suboccipitobregmatic
Answer: A: Suboccipitobregmatic 
Explanation: Ans. A. SuboccipitobregmaticFetal skulla. Mento vertical diameter =14.5cm,b. Submentovertical =11.5cm,c. Sub occipitofrontal =10cm,d. Suboccipitobregmatic =9.5cm (diameter of engagement in vertex presentation),e. Biparietal =9.5cm.