1. The problem asks which of the three curves (green, red, blue) is NOT a function. 2. Recall the definition of a function: For each input $x$, there must be exactly one output $y$. 3. The vertical line test helps determine if a curve is a function: If any vertical line intersects the curve more than once, the curve is NOT a function. 4. Analyze each curve: - Green curve: A vertical line at $x=7$ from $y=-10$ to $y=10$ means multiple $y$ values for one $x$ value. - Red curve: A gently sloping line, passing the vertical line test, so it is a function. - Blue curve: An ellipse centered at the origin, which fails the vertical line test because vertical lines intersect it twice. 5. Conclusion: The green and blue curves are NOT functions because they fail the vertical line test. Final answer: Blue and green only