The height of a dolphin jumping in and out of water, in feet,
can be modeled by the following function, where the x-axis
of the graph is the water line:
f(x) = -0.5x4 + 3.5x3 – 7x2 + 4x.
Which function reveals the moments when the dolphin
enters or leaves the water?

last one.

step-by-step explanation:

last one.

generally speaking, the others follow some sort of pattern that correlates to either linear (looks like a straight line) or sinusoidal (looks like an s).

the last one is just a random cloud of points that doesn't correlate to any particular known order.