Which is a valid velocity reading for an object?
a. 45 m/s
b. 45 m/s north
c. 0 m/s south
d. 0 m/s

Speed and velocity are not the same thing. Velocity is how fast an object is going and its direction. Since the velocity’s formula is distance multiplied to time (seconds), velocity’s unit would be m/s. But velocity needs to be with a direction of where the objects going.
45m/s north and 0m/s south both has the unit that is need and direction. But 0m/s south is not moving at all, yet it does tells us how the object is going that leads us to the appropriate answer, 45m/s north.