Final answer:
A gomphosis is a fibrous joint that connects the teeth to the jaw using fibrous connective tissue. It differs from other joint types like cartilaginous joints (synchondrosis and symphysis) and synovial joints, which are freely movable.
Step-by-step explanation:
A gomphosis is a type of joint where adjacent bones are strongly united by fibrous connective tissue. Specifically, in a gomphosis, the root of a tooth is anchored across a narrow gap by periodontal ligaments to the walls of its socket in the bony jaw. Therefore, the correct answer to the question is that a gomphosis is a (D) fibrous joint.
For added clarification, synchondroses and symphyses are types of cartilaginous joints. A synchondrosis is joined by hyaline cartilage, and a symphysis is where the bones are joined by fibrocartilage. In contrast, synovial joints are freely movable joints with a joint cavity, and are not directly connected by connective tissue or cartilage.