Assuming B is a stoping point that means there is acceleration because acceleration is slowing down to a stop, turning around, or speeding up. Now we also know that its speed is decreasing due to the fact that the dots are getting closser to each other. Its only velocity is it tells a direction and speed so that rules out B and C. All you have left is A and D so, you need to figure out which one has acceleration as slowing to a stop and the speed decreasing. (They kind of walk hand in hand.)
I hope that helped you.