Final answer:
The velocity in which the velocities of two bodies are added is called the resultant velocity.
Step-by-step explanation:
The velocity in which the velocities of two bodies are added is called the resultant velocity.
For example, if the velocity of the first body is 10 m/s in the positive x-direction and the velocity of the second body is 5 m/s in the negative x-direction, the resultant velocity would be 5 m/s in the positive x-direction.
Therefore, the correct answer is a) Resultant velocity.