when you look at the graph you start from the origin and move up the toy car's velocity is constant because its the same rate of position over time
because the only way for the velocity to be zero is if the car has no speed so the answer can't be c , and it can't be A or B because the velocity is still increasing over time so the answer is D because the velocity increases for a will but then it stays the same cause it is at the same position for a while the steadily increases some more. so the Answer is D