Which of the following represents fixed joints?

The correct answer highlights the nature of fixed joints, which are also known as immovable joints. The connection between the skull and teeth falls under this category, as it exemplifies how certain joints provide stability and protection without allowing for any movement. The skull itself is composed of several bones that are fused together, creating a solid structure that houses and protects the brain, while the teeth are firmly anchored in the jawbone, providing stability for chewing and biting functions.

The other options present joints that allow movement, making them not fixed. For instance, the fingers and feet engage in a wide range of motion to facilitate gripping and walking. Similarly, elbows and knees serve as hinge joints that permit bending and extending, and hips and shoulders are ball-and-socket joints that enable extensive ranges of motion in different directions. Understanding the characteristics of different joint types helps clarify why the skull and teeth are classified as fixed joints, marked by their lack of movement and structural stability.