What is the flexible connective tissue that forms the skeleton of sharks?

The correct answer is cartilage, which is the flexible connective tissue that forms the skeleton of sharks. Cartilage is a notochord-derived tissue that is less dense than bone and allows for greater flexibility, which is particularly advantageous for sharks. This adaptation helps them navigate efficiently through water and provides structural support without the weight associated with bony skeletons.

In contrast to sharks, bony fish and most other vertebrates have skeletons primarily composed of bone, which provides rigidity and strength but can be heavier. Tendons and ligaments are types of connective tissue, but they serve different functions; tendons connect muscles to bones, and ligaments connect bones to other bones. They are not involved in the formation of the entire skeletal structure, as cartilage is in sharks.