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
Commonest cause of non engagement at term, in primi is: 
Select and explain. 
A. CPD, B. Hydramnios, C. Brow presentation, D. Breech
A: CPD
Answer: A: CPD 
Explanation: In primi's the most common cause of non engagement at term is deflexed head or occipitoposterior position followed by cephalopelvic dispropoion. Ref: Datta Obs 9e pg 330.