The acceleration of a certain body is 15 m / s2,

this means that :?
1) travels a distance of 15 m in 1 s.
2) it has a constant speed of 15 m / s.
3) for every second of movement it travels 15 m away.
4) its speed changes by 15 m / s for each second of movement.
5) travels a distance of 15 m for every second squared of movement.