Answer: C (-9, 8)
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Step-by-step explanation:
The point (9,8) is in the original set of ordered pairs.
We cannot include (9,-8) since x = 9 is already listed. We can't have repeated x values. If x repeats, then we don't have a function.
This rules out choice A.
Choices B and D are eliminated for similar reasoning.
Choice C can be included because x = -9 hasn't been mentioned yet.
Note: A function is when any given x value leads to exactly one y value.