The correct answer is speed.
The speed of the bullet is defined as the ratio between the distance travelled by the bullet (S) and the time it takes to travel it (t):
[tex] v=\frac{S}{t} [/tex]
This quantity is a scalar quantity, which does not depend on the direction of the bullet. Velocity, however, is a vector quantity, which uses the displacement of the bullet instead of the distance travelled, therefore it takes into account also the direction of the bullet.
