The option that best describes the role the warrior classes played in medieval Japan's economy is:
D. Warriors served the shogun throughout the country, which meant they purchased goods throughout Japan.
Warriors, or samurai, had a significant role in the economy as they often served as local leaders and landholders under the shogunate, and their presence facilitated economic activities by buying and trading goods. They also played a role in maintaining order, which allowed trade and agriculture to flourish.