Which answer choice best describes why the relation is a function or is not a function? Coordinate grid with a horizontal parabola graphed. The relation is not a function because a vertical line intersects the graph more than once. The relation is not a function because a horizontal line will intersect the graph at (0, 0). The relation is not a function because a horizontal line intersects the graph once. The relation is a function because a vertical line could intersect the graph once.