Answer:
The vertical parabola(see attachment)
Explanation:
The relation that is a function must pass the vertical line test.
The vertical parabola will pass the vertical line test.
This means that, a vertical line drawn across the entire graph will intersect the vertical parabola at only one point.
The horizontal parabola, the circle and the vertical line will not pass the vertical line test.
This means that, a vertical line drawn across the entire graph will intersect the graph of these functions at more than one point.