Final answer:
An intangible, in the context of royalty payments, is considered used in the country that enforces protection against unauthorized use, with option 'd. Enforcement' being the correct answer.
Step-by-step explanation:
The student's question pertains to how an intangible is considered used in the context of royalty payments and intellectual property laws. The answer to the question is d. Enforcement. An intangible is considered used in the country that protects the owner against its unauthorized use. The protection and enforcement of intellectual property rights, such as patents and copyrights, are crucial, as these legal instruments provide creators the right to benefit from their work. International efforts through the World Intellectual Property Organization (WIPO) and treaties aim to harmonize the protection of intellectual property across different jurisdictions.