Answer:
The third picture represents a function.
Step-by-step explanation:
The vertical line test is basically making sure that two points do not have the same x-coordinate. In the first graph, the two lines share the same x-coordinates on each point, therefore, it is not a function.
The second picture is a vertical line, and functions cannot be a vertical line, therefore it isnt a function.
In the fourth picture, several points have the same x-coordinate as well.
If you still dont understand the vertical line test, heres an example from the fourth picture:
Point (-2,2) and Point (-2,-2) are both points that fall on the curve. They both have the same x-coordinate, -2. Because of this, the graph cannot be a function. Several other points on the graph also share a same x-coordinate.
Hope this makes sense and helps :)