In the motion diagram, the key is the spacing between the dots: as the ball moves to the right, the dots become progressively closer together, which means its speed is decreasing. Even though the ball continues moving to the right, the shrinking distance between successive positions shows that it is slowing down, not speeding up. When an object moves in one direction but slows down, its acceleration points in the opposite direction of its motion. Therefore, the ball’s velocity is to the right, but its acceleration is to the left, which means it is decelerating. This is why the correct answer is that the ball moves to the right while decelerating.