Concept:Citizenship by descent is acquired through family lineage rather than through place of birth or residence.Explanation:Options A and D describe citizenship by birth or residence, not by descent.Option B is incomplete because the mother being born in the state does not necessarily mean she is a citizen.Option C correctly identifies ancestry, since descent requires that one's parents or grandparents are citizens of the state.Therefore, citizenship by descent depends on the citizenship of one's ancestors.Answer:C. one's grandparents were citizens of that state.