During the defecation reflex, the A)stretch receptors in the rectal walls stimulate parasympathetic motor neurons. B)internal and external anal sphincters relax simultaneously. C)abdominal wall relaxes and the internal abdominal pressure decreases. D)gastroileal reflex moves materials into the rectum through mass peristalsis. E)decreased peristaltic contractions occur in the sigmoid colon and rectum.