What is the domain of the set of ordered pairs?
{(7,-3), (-4,2), (-1,0), (2,-4), (0,-6)}

A. {-6, -4, -3, 0, 2}
B. {-3, -2, -1, 0, 6, 8}
C. D: {All real numbers from -3 to 8}
D. {-4, -1, 0, 2, 7}