Answer:
C
Step-by-step explanation:
A set of coordinates is a function if and only if one input does not map onto two or more different outputs.
In other words, given (x,y), x should each have one distinct y. If an x has 2 or more y, then the y must be the same value.
Choice A:
We see that it has the pairs (1,1) and (1,4). 1 maps onto both 1 and 4, so this is not a function.
Choice B:
Again, we see that it has the pairs (2,2) and (2,5). 2 maps onto both 2 and 5, so this also isn't a function.
Choice C:
In this set, no x are repeated. Thus, this <em>is</em> a function.
Choice D:
In this set, we have the x repeated four times, with 1 mapping onto 2, 3, 5, and 6. Thus, this is not a function.
So, our answer is C.
