Which type of muscle is primarily responsible for voluntary movement?

Skeletal muscle is the type of muscle primarily responsible for voluntary movement. This muscle type is attached to bones and is under conscious control, allowing animals (including humans) to perform intentional movements such as walking, running, or lifting. Skeletal muscle fibers are organized in a striated pattern, which is a distinctive feature that helps differentiate them from smooth and cardiac muscles.

Smooth muscle, on the other hand, is found in the walls of internal organs and is responsible for involuntary movements, such as those in the digestive system and blood vessels. Cardiac muscle, which makes up the heart, is also involuntary and functions automatically to pump blood. Involuntary muscle is a broader term that includes smooth and cardiac muscles, which do not require conscious thought to function. Thus, the defining characteristic of skeletal muscle is its ability for voluntary movement, making it the correct choice for this question.