**Answer: A. Trabeculae**
Spongy bone tissue, also known as cancellous bone, is characterized by its honeycomb-like structure made up of trabeculae, which are thin rods or plates of bone that create a network within the bone. This structure allows for lighter weight while providing strength and support. In contrast, compact bone is dense and structured around Haversian systems (or osteons), which are not present in spongy bone. Therefore, trabeculae is a distinct feature of spongy bone that is not found in compact bone.