When discussing the components of synovial joints, it’s important to note that not all structures are present in every synovial joint. Out of the options provided, c) labrum is the correct answer.
The labrum is a fibrocartilaginous structure that deepens the socket in ball-and-socket joints like the shoulder and hip. However, it is not present in every synovial joint, making it distinct from the articular cartilage, synovial membrane, and articular capsule, which are fundamental components of all synovial joints. The articular cartilage provides a smooth surface for joint movement, the synovial membrane secretes synovial fluid to lubricate the joint, and the articular capsule surrounds and protects the joint, maintaining its stability.