Final answer:
The teres major and teres minor are the main extensors of the glenohumeral joint, with the teres major also assisting in adduction and medial rotation and the teres minor in lateral rotation and extension. So the correct answer is option (C).
Step-by-step explanation:
The main extensors of the glenohumeral joint are not the pectoralis major, latissimus dorsi, deltoid, or rotator cuff muscles. Instead, it's the teres major and the teres minor that actively participate in the extension of the arm at the glenohumeral joint. The teres major assists in adduction and medial rotation of the arm, while the teres minor helps in lateral rotation as well as extension of the arm.
The pectoralis major, latissimus dorsi, and deltoid are more involved in movements like flexion, adduction, and abduction of the arm. The rotator cuff muscles, consisting of the supraspinatus, infraspinatus, teres minor, and subscapularis, primarily provide support for the shoulder joint and assist with rotational movements rather than being primary extensors.