Explanation:
Note: Remember the difference between a scalar and a vector.
A Scalar Quantity has a magnitude (numerical value) only. (Such as Speed, Time, Distance)
A Vector Quantity has a magnitude and a direction. (Such as Velocity, Displacement, Acceleration)
In this case,
B is out as they are of different directions.
A is ruled out too as the direction is different, the resultant velocity will be different as well.
D is ruled out as motion can come in many forms ,such as collision and bouncing.
So therefore answer is C as they have the same magnitude at 100 km/hr.