1. What is the domain of the relation
represented by the ordered pairs (-12, 2),
(-6,4), (0, 6), (3, 7), and (9, 9)?
A. {-12, -6,0,3, 9}
B. {2, 4, 6, 7, 9)
C. {3,9}
D. {-12, -6,0, 2, 3, 4, 6, 7,9}