The graph below does not represent a function because it fails the vertical-line test.
Which is the best explanation of why a graph that fails the vertical line test does not represent a function?
A. If a vertical line intersects a graph more than once, this indicates that there are multiple points with the same y-value. A function cannot have repeated y-values.
B. On a vertical line, one x-value is paired with many y-values. A function cannot have one x-value paired with different y-values, so a vertical line is not a function.
C. The points where a vertical line intersects a graph have the same x-value but different y-values. The graph of a function cannot have points with the same x-value but different y-values.
D. The relation represented by a vertical line maps many x-values to the same y-value. This kind of mapping is not a function. So if a graph intersects a vertical line more than once, that graph is not a function either.