Which relation is a function? A coordinate grid containing a V shaped graph with arrows on the ends of the V and the point of the V is located at the origin. The V shape opens upwards.

A coordinate grid containing a U shape with arrows on both ends that opens to the right. The bottom portion of the U passes through the origin.

A coordinate grid with the graph of a circle centered at the origin and passing through the point begin ordered pair 2 comma 1 end ordered pair.

Coordinate grid with graph of a vertical line at x equals 3.