Answer: C
Step-by-step explanation: The easiest way to determine if a
relation is a function is to use the vertical line test.
The vertical line test tells us that if we can draw a vertical line
that intersects more than one point on the graph of a relation,
then the relation is not a function.
However, in this case, notice that there is no way to draw a
vertical line that intersects more than one point on the graph.
Therefore, this relation must be a function.