To determine whether a graph of a relation is also a function, Shayla declares that the y-axis is a vertical line and counts the number of times that the graph intersects the y-axis. If the graph has exactly one y-intercept, Shayla concludes that the graph shows a function. In all other cases, she declares that it is not a function. Is Shayla applying the vertical line test correctly? No, because the y-axis is a horizontal line. No, because using the y-axis tests only whether x = 0 is mapped to multiple values. Yes, because multiple y-intercepts represent multiple x-values being mapped to y = 0. Yes, because the y-axis represents all vertical lines of the x-values.