A student investigates the motion of a toy car accelerating down a runway. They record the velocity v v\,v at several intervals of time t t\,t and plot the results, drawing a line of best fit.

Which option best describes the relationship shown by these results?
vvv is directly proportional to ttt.
There is a linear relationship between vvv and ttt, but they are not directly proportional.
vvv is inversely proportional to ttt.
vvv is proportional to t2t^2t2.