Answer: A
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.
In this case, the only graph that is not a function is A.
If we draw a vertical line on the graph, it's possible that
the lie will hit two points on the graph telling us that it's not a function.
