<prompt> All but one are true regarding levator ani musleLevator ani muscles constitute pelvic diaphragmContraction of levator pulls rectum and vagina towards symphysis pubisInsertion of the muscle is fixedInternal rotation of presenting part during delivery is assisted by levator muscles  <response>: 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. 