Final answer:
Cartilage, a dense connective tissue (option A) , is vital for joint function in the skeletal system, providing flexibility, smooth movement, and support by cushioning between bones at synovial and cartilaginous joints.
Step-by-step explanation:
Cartilage is a type of dense connective tissue that is integral to the skeletal system. Cartilage provides both flexibility and support within the body's joints, enabling smooth movement and offering cushioning between bones to prevent friction.
Located in areas of the skeleton such as the ribcage and at the ends of long bones at synovial joints, cartilage can be either hyaline cartilage or fibrocartilage, depending on the joint type. For example, a synchondrosis is a joint where the bones are joined by hyaline cartilage, while at a symphysis, the bones are united by fibrocartilage.
In addition to providing flexibility, cartilage also serves to unite adjacent bones at cartilaginous joints, lacking a joint cavity. Thus, cartilage is essential for the proper function and protection of joints, and is a key structural component of the skeletal system.