What is one of the amendments that define voting eligibility?

One of the amendments that defines voting eligibility is that citizens who are 18 years of age and older have the right to vote. This is established by the 26th Amendment to the United States Constitution, ratified in 1971, which specifically prohibits the federal and state governments from denying the right to vote to citizens aged 18 years or older based on age. This amendment was significant in expanding access to voting, particularly during a time when younger people were actively participating in social and political movements.

The other choices either reflect outdated standards or criteria that are not universally applied in determining voting eligibility. For example, specifying citizens 21 and older refers to the previous voting age before the ratification of the 26th Amendment. Similarly, considerations like felony records or literacy tests do not uniformly determine voting eligibility across the board and have been challenged in various legal contexts as discriminatory practices.