Which function of the skin keeps bacteria from entering the body?

Rationale:
A. The shoulder joint (glenohumeral joint) is the most mobile joint in the body, allowing a wide range of motion. Its shallow socket and relatively weak ligament support make it more susceptible to dislocation.
B. Knee is a strong hinge joint stabilized by ligaments and muscles, making dislocations less common than in the shoulder.
C. Hip is a deep ball-and-socket joint with strong ligaments and surrounding muscles, making dislocation rare except in severe trauma.
D. Elbow is a hinge joint with strong ligamentous support, so dislocations are less frequent compared to the shoulder.

Rationale:
A. Flexion is a movement that decreases the angle between two bones at a joint. It often involves bending a limb, such as bending the elbow or knee, or moving the chin toward the chest at the neck. Flexion brings body parts closer together and is a fundamental movement in many joints.
B. The opposite of flexion, extension increases the angle between two bones, straightening a joint. For example, straightening the elbow after it has been bent is extension.
C. This is the movement of a body part toward the midline of the body, such as bringing the arm down to the side from a raised position. It does not specifically decrease the angle at a joint.
D. This is the movement of a body part away from the midline, such as lifting the arm or leg out to the side. Like adduction, it is not about decreasing the angle at a joint.