What happens when voters are out of state on election day?
a they must wait until the next election to vote.
b they must register again to vote.
c they must vote at a local polling place.
d they must vote using an absentee ballot.

D, they must vote using an absentee ballot. A is definitely not correct, because no citizen is denied the right to vote given that they are at the right age. B isn't correct because one will not be punished for not exercising a right. And C isn't correct because votes are counted in the electoral college, and the amount of electors are tied proportionally to the quantity of people in the Senate and in the House. The latter of those two is based on population, so that would be messing with the system. So, D is the only answer, which logical due to it being an "absentee" ballot, or someone who is absent.