Which of the following statements is true about fibrous joints?

Fibrous joints are characterized by the way they connect bones. They are joined by dense connective tissue that is rich in collagen fibers, which provides stability without allowing significant movement. This lack of movement is an essential feature that distinguishes fibrous joints from other types, such as synovial joints, which allow a greater range of motion.

In contrast, the other options describe features that do not align with the nature of fibrous joints. For instance, the assertion that fibrous joints are highly flexible and movable clearly contradicts their fundamental property of limited or no movement. The mention of an articular cavity is specific to synovial joints, not fibrous joints, which do not possess such cavities. Lastly, the idea that fibrous joints are found solely in the pelvic area is incorrect, as these joints can be located in various parts of the body, including the sutures of the skull and the connections between certain long bones.