Answer:
C
Explanation:
A function cannot have multiple y values for one x value.
Option A lists the y values of -8 and 10 for the x value of -4. Therefore this is not a function.
Option B lists 0, 5, 10, AND 15 all for -1. This can't be a function either.
Option C does not have two of the same x values for different results. Although both 0 and 9 give you the answer of 1 for the y value, this is perfectly okay in a function. This is your answer.