Which of the following is connective tissue that is attached to bones at the joints?

The correct choice is cartilage. This is because cartilage is a flexible connective tissue found in various parts of the body, including joints. It acts as a cushion between bones, allowing for smooth movement and reducing friction during joint activity. In a joint, cartilage covers the ends of bones, providing a slick surface that facilitates movement and absorbs shock, thus playing a crucial role in joint function.

While ligaments and tendons are also types of connective tissues associated with the musculoskeletal system, their functions differ. Ligaments connect bones to other bones, providing stability to joints. Tendons, on the other hand, connect muscles to bones, enabling movement when muscles contract. Stroma refers to the supportive tissue in an organ, but it does not specifically relate to joints like cartilage does. Therefore, cartilage is the most accurate answer in the context of connective tissue that is directly involved at the joints.