Which relation is NOT a function?

A circle centered at the origin

A function $f(x)$ gives gallons of fuel after $x$ minutes, with $y$-intercept $(0, 15)$ and $x$-intercept $(5, 0)$. What does the $x$-intercept mean?

The tank is empty after 5 minutes

Vertical stretch by 3 and reflection across the x-axis

12questions. Pick an answer and you'll see why right away.

If $f(x) = 4x - 5$ , what is $f(3)$ ?
Which relation is NOT a function?
A graph runs from the point $(-3, 0)$ to $(2, 10)$ with both endpoints included. What is the domain?
A function $f(x)$ gives gallons of fuel after $x$ minutes, with $y$ -intercept $(0, 15)$ and $x$ -intercept $(5, 0)$ . What does the $x$ -intercept mean?
A downward parabola has vertex $(4, 20)$ . What is the maximum value of the function?
For $f(x) = x^{2} - 3$ , what is the average rate of change from $x = 1$ to $x = 5$ ?
A runner's distance is 300 m at 2 min and 900 m at 5 min. What is the average rate of change?
The graph of $g(x) = f(x) + 4$ is the graph of $f$ transformed how?
Starting from $y = x^{2}$ , what is the vertex of $y = (x - 5)^{2} + 2$ ?
The graph of $g(x) = -3 f(x)$ differs from $f$ how?
Function A is $f(x) = 6x + 1$ . Function B's table is $(0, 2), (3, 11)$ . Which has the greater rate of change?
Which describes the domain of a function giving the number of tables needed to seat $g$ guests?