What is the domain of the following set of ordered pairs?
{(-2,-5), (-3,8), (12,6), (8, -3), (4,0), (-5, -7)}
○ a. {-5, 8, 6, -3, 0, -7}
O b. {-2, -5, -3, 8, 12, 6}
○ c. {8, −3, 4, 0, − 5, −7}
O d. {-2, -3, 12, 8, 4, −5}