Which amendment instituted prohibition?

The Eighteenth Amendment to the United States Constitution is the correct choice because it established the prohibition of alcoholic beverages in the United States. Ratified in 1919 and going into effect in 1920, this amendment made it illegal to manufacture, sell, or transport intoxicating liquors. The intent behind the Eighteenth Amendment was to reduce crime and corruption, improve health and hygiene, and promote moral values. However, this period of prohibition led to a range of unintended consequences, including an increase in organized crime related to the illegal trade of alcohol, which highlighted the challenges of enforcing such a ban.

The other amendments mentioned do not relate to the institution of prohibition. The Twenty-first Amendment, for instance, actually repealed the Eighteenth Amendment, thereby legalizing alcohol once more. The Ninth Amendment addresses rights not specifically enumerated in the Constitution, and the Fourth Amendment deals with protection from unreasonable searches and seizures, neither of which pertain to the prohibition of alcohol. These distinctions clarify why the Eighteenth Amendment is indeed the historical legal basis for the prohibition era in the United States.