Answer:
D) The y-axis only tests whether x = 0 has been mapped to more than one y coordinate.
Explanation:
The y-axis is a vertical line and intersects the x-axis (horizontal line) at the origin (0, 0) when both x and y are zero.
Vertical line test
A graph represents a function if and only if all vertical lines intersect the graph at most once.
Therefore, the strategy of using only the y-axis as the vertical line in the vertical line test is flawed because the y-axis only tests whether x = 0 has been mapped to more than one y-coordinate.