**Core Concept**
The Controlled Substances Act (CSA) of 1970, as amended by the Controlled Substances Act Amendments of 1984, is a federal law in the United States that regulates the production, distribution, and use of controlled substances. The CSA divides controlled substances into five schedules based on their potential for abuse, accepted medical use, and potential for dependence. The CSA also established the Drug Enforcement Administration (DEA) to enforce the law.

**Why the Correct Answer is Right**
COPRA, or the Comprehensive Omnibus Reform Act, is a federal law that was enacted to reauthorize and amend the Controlled Substances Act (CSA). The law was intended to strengthen the DEA's authority to enforce the CSA and to provide additional tools for the agency to combat the diversion of controlled substances. The law also made significant changes to the scheduling of controlled substances, including the creation of a new schedule for fentanyl and its analogs.

**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect because the CSA was enacted in 1970, but it was not reauthorized until 1984.
**Option B:** This is incorrect because the CSA Amendments of 1984 did not come into existence on their own, but rather were enacted as part of the Comprehensive Omnibus Reform Act (COPRA).
**Option C:** This is incorrect because COPRA was enacted in 1984, not in the 1990s or 2000s.

**Clinical Pearl / High-Yield Fact**
The Comprehensive Omnibus Reform Act (COPRA) of 1984 made significant changes to the Controlled Substances Act, including the creation of a new schedule for fentanyl and its analogs, and the establishment of the DEA's authority to regulate the production and distribution of controlled substances.

**Correct Answer: C. 1984.**