Which type of muscle is involuntary and not under conscious control?

The correct answer is based on the fact that both cardiac and smooth muscles are indeed involuntary and not under conscious control.

Cardiac muscle, which makes up the heart, operates automatically and rhythmically to pump blood throughout the body; its contractions are controlled by the heart's intrinsic conduction system. This function is essential for survival, as it allows the heart to beat without the need for conscious thought or direction.

Smooth muscle, found in the walls of hollow organs such as the intestines and blood vessels, also operates involuntarily. It helps facilitate movement within these organs through processes like peristalsis and vasoconstriction, importantly governing functions necessary for digestion and circulation without conscious control.

In contrast, skeletal muscle is the type of muscle that is under voluntary control, meaning individuals can consciously direct its movement, such as when lifting weights or walking. Therefore, the correct identification of cardiac and smooth muscles as involuntary is what validates the choice that includes both.