This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Physiology
Ha's rule is related to 
Select and explain. 
A. Mechanism of Internal rotation, B. Mechanism of Crowning, C. Mechanism of Engagement, D. Mechanism of Restitution
A: Mechanism of Internal rotation
Answer: A: Mechanism of Internal rotation 
Explanation: Elastic recoil of Levator Ani occurs bringing the occiput forwards in the midline. The process is repeated until the occiput is placed anteriorly. This is called as rotation by law of pelvic floor- Ha's rule.