Which table represents y as a function of x and explain?

For a function a x value cannot have more than 1 corresponding y value
So for example, A, has the x value 1 which has the y values 1 and 5, so because it has multiple x values it is not a function.

So the answer is C

This can be proved because,
8 only has one corresponding y value (-1)
7 only has one corresponding y value (2)
6 only has one corresponding y value (-1)
5 only has one corresponding y value (2)
and 4 only has one corresponding y value (-1)

Each x factor has a unique y factor, making answer choice C a function.