Answer:
Graphs 1, 2, and 3 are not functions. Graph 4 is a function.
Step-by-step explanation:
Use the vertical line test.
Imagine a vertical line moving from left to right.
If in any position of the vertical line, it intersects more than one point on the graph, then it is not a function.
In graphs 1 and 2 it is clear that there are many vertical lines than would intersect the graph at more than one point.
In graphs 3, a vertical line would intersect the vertical parts of the graph at more than 1 point, so graph 3 is not a function.
The only function is graph 4.
