1. Which muscle is primarily responsible for the abduction of the shoulder? A. Deltoid B. Teres major C. Latissimus dorsi D. Pectoralis major Answer: A. Deltoid Rationale: The deltoid muscle, due to its location and fiber direction, is the primary abductor of the shoulder, lifting the arm away from the body. 2. The triceps brachii muscle extends the forearm at the elbow joint. Which head of the triceps brachii is most active during this action? A. Long head B. Lateral head C. Medial head D. All heads equally Answer: D. All heads equally Rationale: All three heads of the triceps brachii contribute to forearm extension, with no single head playing a more significant role in the action. 3. In a patient with a rotator cuff injury, which movement would likely be the most difficult? A. Elbow flexion B. Shoulder adduction C. Shoulder external rotation D. Wrist extension Answer: C. Shoulder external rotation Rationale: The rotator cuff muscles, particularly the infraspinatus and teres minor, are key in shoulder external rotation. An injury to these muscles would impair this movement. 4. Which muscle is not part of the quadriceps femoris group? A. Vastus lateralis B. Vastus medialis C. Vastus intermedius D. Biceps femoris Answer: D. Biceps femoris