Answer:
C. C{(6,-9),(<u><em>-3</em></u>,6),(<u><em>-3</em></u>,-7),(-9, -2)}
Step-by-step explanation:
If you see the same x-coordinate used more than once, it is not a function.
Here, you only see this in choice C, where x = -3 for two points. That makes this relation not a function.