Answer:
Choice A.
Step-by-step explanation:
Apply the vertical line test.
If a vertical line intersects 2 or more points on the graph, the relation is not a function.
If all vertical lines intersect at most 1 point on the graph, the relation is a function.
Any vertical line in Choice A. intersects 1 single point. Choice A. is a function.
There are vertical lines that would intersect 2 points of the graph in Choices B., C., and D., so they are not functions.
