question: What shape are the muscles that control the anus?
distractor3: triangular
distractor1: elliptical
distractor2: irregular
correct_answer: circular
support: Circular muscles control the anus. They relax to let the feces pass out of the body through the anus. After feces pass out of the body, they are called stool. Releasing the stool from the body is referred to as a bowel movement.