I need help please. I think its C but i want to be sure!

Is this relation a function? Justify your answer.

A. No, because two points with the same x-value have different y-values.

B. Yes, because every x- and y-value is positive.

C. Yes, because the number of x-values is the same as the number of y-values.

D. No, because two points with the same y-value have different x-values.