The role of the samurai in feudal Japan is best represented by option c. Samurai were primarily warriors who not only served the landholding daimyo but also played a significant role in the military conflicts of the time. While they did serve the daimyo (option b) and were integral to the feudal system as elite warriors, their interest in battles and the need for protection and governance often contributed to the frequency of conflicts in feudal Japan.
However, to clarify, samurai did not own most of the land (option a); that was typically the role of the daimyo. And while samurai were indeed warriors, the assertion that they protected Japan without the use of weapons (option d) is not accurate, as their primary identity was that of armed combatants.