Answer:
D
Step-by-step explanation:
A function is where each input (here, the input is x) corresponds to exactly one output (here, the output is y). In other words, if a function is graphed, we should be able to draw a vertical line through every single part of it that will intersect it at only one place.
Let's examine each choice.
(A) Well, if we draw a vertical line through the graph, it will obviously intersect the entire line - which is an infinite number of intersections, so this is not a function.
(B) If we draw a vertical line through the portion of the graph that lies near the positive x-axis, we note that it will intersect twice, so this is not a function.
(C) If we strategically draw a vertical line through the y-axis, we see it will intersect two times, so this is not a function.
(D) We can draw a vertical line through any portion of this graph and know that it will only intersect once.
Therefore, the answer is D.
