Final answer:
The large lymphatic capillaries in a lymph node spanned by reticular fibers are known as sinuses.
Step-by-step explanation:
The correct answer to the question is A) Sinuses. In lymph nodes, large lymphatic capillaries spanned by crisscrossing reticular fibers are known as sinuses. Specifically, lymph enters a lymph node via the subcapsular sinus, which contains those reticular fibers along with dendritic cells and macrophages. Lymph then continues to travel through the node, where it passes through the cortex of the lymph node containing lymphoid follicles with germinal centers of rapidly dividing B cells, and finally reaches the medullary sinuses before exiting the node through efferent lymphatic vessels.