use the vertical line test to determine if the graph is a function or not a function.

Explanation:

Step1: Recall the vertical line test

If a vertical line intersects the graph at more than one point, the graph is not a function.

Step2: Analyze the first graph

A vertical line can intersect the first graph at more than one point. So, it is not a function.

Step3: Analyze the second graph

A vertical line can intersect the second graph at more than one point. So, it is not a function.

Step4: Analyze the third graph

For any vertical line drawn, it will intersect the third graph at most one point. So, it is a function.

Answer:

First graph: not a function; Second graph: not a function; Third graph: function.