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: Gynaecology & Obstetrics
The prerequisites for internal rotation of the head are all except 
Select and explain. 
A. Well flexed head, B. Efficient uterine contraction, C. Favourable shape of the pelvis, D. Tone of the abdominal muscles
D: Tone of the abdominal muscles
Answer: D: Tone of the abdominal muscles 
Explanation: The shape of pelvic floor: Two halves of levator ani form a gutter and viewed from above the direction of fibers is backward and towards the midline. Elastic recoil of the levator ani occurs bringing the occiput forwards towards the midline.Pelvic shape: forward inclination of the side walls of the cavity, narrow bispinous diameter and long anteroposterior diameter of outlet pulls long axis of the head to accommodate in maximum available diameter,Well flexed headEfficient uterine contractionMid-pelvic plane shapeThe tone of levator ani musclesD.C.DUTTA&;S TEXTBOOK OF OBSTETRICS, Pg no:125, 7th edition