What is the main criterion for the eligibility to vote in Illinois?

The main criterion for eligibility to vote in Illinois is that a person must be a U.S. citizen, a resident of Illinois, and at least 18 years of age. This foundational requirement aligns with federal standards that dictate voting rights and access to the electoral process.

Being a U.S. citizen ensures that only those who are legally recognized as part of the nation are allowed to participate in democratic processes. Residency in Illinois indicates an individual's connection to the state and a vested interest in its governance and policies, while the age requirement of at least 18 years ensures that voters are deemed mature enough to make informed decisions regarding the direction of their community and the nation as a whole.

The other options present criteria that do not reflect the actual voting laws in Illinois. For example, employment or property ownership is not a requirement for voting, nor is a specific residency duration such as five years. Therefore, the correct answer encompasses the essential criteria that define voting eligibility in the state.