Final answer:
Golgi and Ramón y Cajal received the 1906 Nobel Prize in Medicine for their work on the nervous system's structure.
Step-by-step explanation:
Camillo Golgi and Santiago Ramón y Cajal were jointly awarded the Nobel Prize in Physiology or Medicine in 1906 for their significant advancements in understanding the structure of the nervous system. Camillo Golgi developed a staining technique that revealed the network of vesicles now known as Golgi bodies in nerve cells. Santiago Ramón y Cajal reported and illustrated the structure of neurons and their nuclei in hand-drawn micrographs. Golgi developed a staining technique that allowed the visualization of what we now call the Golgi apparatus, while Ramón y Cajal's detailed drawings of neurons greatly contributed to neuronal theory. Their discoveries in cellular neuroscience were foundational in the study of the nervous system's histology.
Answer: C) Advancements in understanding the structure of the nervous system.