What is the longest bone in the human body?

Rationale:
A. Cartilaginous joints are connected entirely by cartilage (such as the pubic symphysis or intervertebral discs). They allow limited movement but do not make up the majority of joints in the body.
B. Fibrous joints are connected by dense connective tissue and are mostly immovable (such as sutures in the skull). They are important for stability but are relatively few compared to synovial joints.
C. Synovial joints are the most numerous type in the body and allow the greatest range of motion. Examples include the shoulder, hip, knee, and elbow. They are characterized by the presence of a joint cavity filled with synovial fluid, articular cartilage, a synovial membrane, and supporting ligaments. Their structure allows movements such as gliding, rotation, flexion, extension, abduction, and adduction.
D. Synarthroses refers to immovable joints (such as sutures), which are a subset of fibrous joints. They provide stability but are not the majority type of joint in the body.

Rationale:
A. This would mean closer to the body surface. The dermis is not superficial; rather, the epidermis is the most superficial layer of the skin.
B. This refers to being closer to the midline of the body. The term “medial” does not describe the relationship between the dermis and epidermis.
C. This refers to being away from the midline of the body. Like “medial,” it is not appropriate to describe the layers of the skin.
D. The dermis lies directly beneath the epidermis, making it deeper in position. It contains connective tissue, blood vessels, hair follicles, sebaceous glands, sweat glands, and sensory receptors that support and nourish the epidermis.