Peristalsis is achieved through involuntary contraction of which muscle?

Peristalsis is a coordinated, involuntary muscle contraction process that moves food through the digestive tract. This process is primarily facilitated by smooth muscle, which is found in the walls of the gastrointestinal tract. Unlike skeletal muscle, which is under voluntary control and responsible for movements that we consciously initiate, or cardiac muscle, which makes up the heart and operates through involuntary contractions to pump blood, smooth muscle operates automatically and reflexively to facilitate peristaltic movement.

Smooth muscle cells are organized in layers and can contract rhythmically without conscious effort. This inherent ability to contract and relax in a synchronized manner enables the smooth muscle to push contents through the digestive system efficiently. Therefore, peristalsis, being a function of the smooth muscle, is what makes choice "C" the correct answer for this question. The voluntary nature of skeletal muscle and the specialized function of cardiac muscle align it outside the context of peristaltic action in the digestive system.