PLEASE HELP!!

What is the domain of the function {( −2, 1), ( −1, 3), (0, 2), (1, 0)}?

A. {0, 1}
B. {0, 1, 2, 3}
C. {−2, −1, 0, 1}
D. {−2, −1, 0, 1, 2, 3}