Final answer:
The U.S. Congress responded to the Catfish farmers' issue by placing high tariffs on imported Vietnamese catfish to ensure the competitiveness of U.S. farmers, an action aligned with anti-dumping measures.
Step-by-step explanation:
The Catfish case in question refers to a situation where U.S. Catfish farmers were affected by the importation of cheaper catfish, primarily from Vietnam. To address this issue, the farmers sought legislative support from Congress. The correct answer to what the U.S. Congress did in response is d. Place high tariffs on imported catfish coming from Vietnam to keep U.S. catfish farmers competitive on price. This action is aligned with anti-dumping measures, where tariffs are imposed to prevent imports sold below the cost of production, which is considered unfair trade under World Trade Organization (WTO) rules and can lead countries to file an anti-dumping complaint with the WTO.