Students use a stretched elastic band to launch carts of known mass horizontally on a track. The elastic bands exert a force F, which is nonlinear as a function of the distance x that the band is stretched. A meter stick is used to measure x, and a motion detector is used to measure the resulting maximum speed of the carts. This procedure is repeated to gather data for several different values of x. Which of the following graphs, if linear, supports the hypothesis that F is a function of x^2?

a. A graph of the cart's maximum speed as a function of x
b. A graph of the cart's maximum speed as a function of x^2
c. A graph of the cart's maximum speed squared as a function of x
d. A graph of the cart's maximum speed squared as a function of x^2
e. A graph of the cart's maximum speed squared as a function of x^3