In the above examples, the only one that is not an example of speed is the option:
"6 miles per hour north". A speed doesn't have a direction added to it. If a statement has a direction added to it, it's velocity, not speed. Speed is a scalar quantity. In other words, it is the rate at which the object covers the distance. Speed does not care about direction. It is also not aware of direction. Velocity, on the other hand, is aware of direction and of speed.
