Answer:
D
Explanation:
the "vertical line test" is a test you can do on a graph. Basically, draw a vertical line anywhere in the function. Now, ask yourself, "how many points does the vertical line hit on the graph?"
if the answer is only one, then that means that the graph is a function. However, if it's more than one, that means that it's not a function.
In this question, if you draw a vertical line, you will see that it only hits one point. Therefore it is a function.
Confused why the vertical line test works?
In a function, the x values CANNOT repeat. A vertical line represents a line where only the x value is present (no slope, no y intercept), so if hits more than one line on the graph, that shows that the x value repeated, so it's not a function.
there is no "horizontal line test" because a horizontal line represents where only they value is present and y values CAN repeat in a function.
Hope this helps!