Answer:
A train travels due west at 90 km/h.
Explanation:
In order to give the complete description of velocity, we need to recall that velocity is a vector quantity. We must have both magnitude and direction for a vector quantity.
Since, velocity is a vector, it should have both magnitude and direction.
The magnitude of velocity is given in km/h or m/s.
Here, only the first option has magnitude of 90 km/h and direction as west.
So, the first option is the correct one.