What is true about opposition in thumb movement?

Opposition in thumb movement specifically refers to the unique action where the thumb touches the fingertips of the same hand. This movement is essential for grasping and manipulating objects, allowing for a strong pinch grip and fine motor skills. The movement involves a combination of flexion and rotation at the carpometacarpal joint of the thumb, enabling the tip of the thumb to reach across the palm to touch the fingers.

This movement is crucial in numerous daily activities, such as writing, picking up small objects, or buttoning clothing. The thumb's ability to oppose enhances hand function significantly, distinguishing humans and some primates from many other species that do not possess this ability.

In contrast, options referring to rotation of the wrist or side movements of the thumb relate to other types of movement and do not accurately describe the opposition of the thumb. The mention of touching the pinky with the thumb does not represent the full range of opposition, as opposition can occur with any finger, not just the pinky. Thus, the correct answer highlights the specific action that defines thumb opposition.