The domain of the following relation: R {(6, -2), (1, 2), (-3, -4), (-3, 2)} is
{-3, -3, 1, 6}
{-4, -2, 2, 2}
{-4, -2, 2}
{-3, 1, 6}
{-3, -3, 1, 6}
{-4, -2, 2, 2}
{-4, -2, 2}
{-3, 1, 6}