Here's a problem to solve: A student is standing on a skateboard that is not moving. The total mass of the student and the skateboard is 50 kilograms. The student throws a ball with a mass of 2 kilograms forward at 5 m/s. Assuming the skateboard wheels are frictionless, how will the student and the skateboard move?

Among the 4 following options, which is the correct answer?

- A: forward at 0.4 m/s
 
- B: forward at 5 m/s
 
- C: backward at 0.2 m/s
 
- D: backward at 5 m/s
 