Final answer:
The projections formed where bones articulate with each other are referred to as articulations, specifically known as fossae, which are depressions on the bones that serve as articular surfaces for joints.
Step-by-step explanation:
The projections formed where bones articulate with each other are known as articulations. These bone surfaces come together at joints, conforming to one another; for example, one being rounded and the other cupped, to enhance the function of the articulation. The correct answer to the question is option a) Fossae, as these are the depressions found on bones where the articular surfaces are located. Areas of bones that project above the surface are known as projections, which serve as attachment points for tendons and ligaments, reflecting the forces exerted on them. Openings or grooves in the bone, like foramina, allow the passage of blood vessels and nerves.