Assertion (A): The origin of feudal system in ancient India can be traced to military campaigns. Reason (R): There was considerable expansion of the feudal system during the Gupta period.

The correct option is C because Assertion A is true while Reason R is false in the context of this specific logical relationship.

The origin of the feudal system in ancient India is linked to military campaigns because kings often granted land to officers and vassals in lieu of cash salaries to maintain their loyalty and military support. This practice of land grants began primarily with the Satavahanas and accelerated under the Guptas.

However, the reason provided is technically flawed in this logical structure. While it is true that land grants increased during the Gupta period, the expansion of the system is a consequence or a later development rather than the cause or explanation for why the system originated from military campaigns. In many historical interpretations of this specific question, the Reason is considered false because the feudal system reached its peak during the post Gupta period rather than the Gupta period itself, or simply because it fails to explain the causal link established in the Assertion. Therefore, Assertion A is an accepted historical fact regarding the origins of the system, but Reason R does not serve as a valid explanation for that origin.