Which of the following muscles is found in the lower extremity?

The sartorius muscle is indeed found in the lower extremity. It is the longest muscle in the human body and runs down the length of the thigh, originating from the anterior superior iliac spine of the pelvis and inserting on the medial side of the tibia. The sartorius muscle plays a crucial role in the flexion, abduction, and lateral rotation of the hip, as well as assisting with flexion of the knee. This unique positioning and function in the lower body categorize it specifically as a lower extremity muscle.

In contrast, the biceps muscle is primarily located in the upper arm, responsible for flexing the elbow and rotating the forearm. The triceps muscle, also situated in the upper arm, functions to extend the elbow. Lastly, the deltoid muscle is found in the shoulder area, facilitating movements of the arm. Each of these other muscles serves distinct purposes in the upper body, confirming that the sartorius is the only correct option associated with the lower extremity.