#### Answer

The $\underline{\text{
vertical line test
}}$ is used to determine whether a graph is that of a function. It says that any vertical line can intersect the graph of a(n) $\underline{\text{
function
}}$ in no more than one point(s).

#### Work Step by Step

If a vertical line drawn anywhere intersects the graph at only 1 point, then it is a graph of a function.