Which amendment defines the legal drinking age in the United States?

The Twenty-First Amendment is significant because it repealed the Eighteenth Amendment, which had established Prohibition in the United States. Following the repeal, the Twenty-First Amendment effectively allowed states to determine their own laws regarding the sale and consumption of alcoholic beverages. This led to the establishment of legal drinking ages, which vary by state but generally became standardized at 21 years old in the 1980s when Congress passed the National Minimum Drinking Age Act. This Amendment is essential in understanding how federal and state powers interact regarding alcohol regulation.

The other amendments mentioned do not relate to the legal drinking age; they cover different issues, such as presidential term limits, representation in the Electoral College for Washington D.C., and voting rights. Thereby, the Twenty-First Amendment is directly linked to the regulation of alcohol and the legal drinking age in the United States, making it the correct answer.