Final answer:
The pectoralis major is the only scapular muscle that flexes and adducts the arm.
Step-by-step explanation:
Of all the scapular muscles, the only one that flexes and adducts the arm is the pectoralis major. The pectoralis major is a large, fan-shaped muscle located in the chest region. It has two heads, the clavicular head, and the sternal head, which converge to form a single muscle belly. The clavicular head primarily assists in flexing the arm, while the sternal head aids in adduction. Working together, these actions allow the pectoralis major to play a significant role in movements like hugging, pulling objects toward the body, and various pressing motions. It is a key muscle involved in upper body strength and functional activities.