Final answer:
Moving the shoulder through flexion and extension involves decreasing and increasing the angle between the bones at the shoulder joint, corresponding to option 3) Flexion and extension.
Step-by-step explanation:
When a client is moving their shoulder through flexion and extension, they are performing movements in the sagittal plane where flexion reduces the angle between the bones at a joint, and extension increases the angle between the bones. In the context of the shoulder, these movements are occurring at the glenohumeral joint, which is a multiaxial ball-and-socket joint, allowing for a wide range of motion including flexion/extension, abduction/adduction, circumduction, and medial/lateral rotation. Therefore, the movement of the shoulder in this case is option 3) Flexion and extension.