All but one are true regarding levator ani musle: (A) Levator ani muscles constitute pelvic diaphragm, (B) Contraction of levator pulls rectum and vagina towards symphysis pubis, (C) Insertion of the muscle is fixed, (D) Internal rotation of presenting part during delivery is assisted by levator muscles
Answer is C. The origin of levator muscle is fixed because muscle arises anteriorly from bone (pubis) and is inserted into anococcygeal raphe or coccyx, both of which are moveable.