Which type of muscle contraction is involuntary and found in internal organs?

The type of muscle contraction that is involuntary and found in internal organs is smooth muscle contraction. Smooth muscle tissue lacks the striations seen in skeletal and cardiac muscle, which is why it is called "smooth." This muscle type is found in the walls of hollow organs such as the intestines, blood vessels, and the bladder, where its involuntary contractions help facilitate bodily functions like digestion and circulation.

In contrast, skeletal muscle contraction is under voluntary control and is responsible for movements of the skeleton. Cardiac muscle contraction occurs in the heart and is also involuntary but is specialized for the rhythmical contractions needed to pump blood. Striated muscle contraction refers to both skeletal and cardiac muscles due to their striated appearance but does not apply to the involuntary contraction context associated with smooth muscle. Therefore, smooth muscle contraction is the only one among the choices that fits the characteristics of being involuntary and located in internal organs.