The correct answer is Patella.

A sesamoid bone is a small, round bone that is embedded within a tendon. These bones typically develop in response to strain and serve to protect the tendon, as well as increase its mechanical advantage by altering the direction of muscle forces.

- The Patella is the largest and most well-known sesamoid bone in the human body. It is located within the tendon of the quadriceps femoris muscle and plays a crucial role in knee extension by improving leverage.

- The Pisiform is also a sesamoid bone, but it is often considered a specialized carpal bone located within the tendon of the flexor carpi ulnaris in the wrist. However, in many educational contexts, the patella is the primary example.

- The Scaphoid and Talus are irregular bones that belong to the carpal and tarsal groups respectively, and are not categorized as sesamoid bones.

In summary, while other bones listed have unique structural roles, the Patella best fits the definition of a sesamoid bone because of its position within a tendon and its biomechanical function.

Reference: Gray's Anatomy, 41st Edition, Volume 1, Chapter 15 – Bones of the Lower Limb