Smooth muscle is the correct answer because it is a type of muscle tissue found in the walls of hollow organs, such as the intestines, blood vessels, and uterus. It is called "smooth" muscle because it lacks the striations or bands that are present in skeletal and cardiac muscle. Smooth muscle is involuntary, meaning it is not under conscious control, and is responsible for various bodily functions such as digestion, blood flow regulation, and labor contractions.