Velocity = (distance covered in a direction) / (time to cover the distance)
Since the y-axis is position (distance), the speed at 3 seconds is the slope of the graph at 3 seconds, and NOT its y-value.
The slope is fairly easy to pick off, because the graph is so straight from 2 sec to 5 sec. During that time, the distance shrinks by 10 meters (from 10m to zero). So the slope of that whole piece of the graph is (-10m) / (3 sec).
That's a slope of (10/3 m/s) or 3.33 m/s .
In answer to the question, we can only give the speed at 3 sec, not the velocity, since we have no information about the direction of the motion. Consequently, I would call the speed a positive number. But it's not worth arguing about, so you should just select choice-A and not make a big scene.
