What is the domain of the following relation?
{(-3, -8), (-2, 9), (1, -1), (5,3)}
O {-8, -1, 3, 9}
O {-3, -2, 1, 5}
O (-3, -8)
O {-8, -3, -2, -1, 1, 3, 5, 9}