The correct answer is A. Acetabulum and femoral head
Explanation:
The hip joint is a bone structure that connects the pelvis to the femur (leg). This structure is classified as a ball and socket joint because it includes a spherical bone structure that fits in a spherical depression. In this context, the hip joint is composed of to main sections, the first one is the femoral head that acts as the ball of the joint and is attached to the femur and the second one is the acetabulum that acts as the cavity or "socket" of the joint. According to this, the pair of structures in the hip joint is "Acetabulum and femoral head".
