Well, st first we should find <span>initial momentum for the first person represented in the task which definitely must be :
</span>

And then we find the final one :

Then equate them together :
So we can get the velocity, which is

In that way, according to the main rules of <span>conservation of momentum you can easily find the solution for the second person.
Regards!</span>
Answer:
We have learned that refraction occurs as light passes across the boundary between two media. Refraction is merely one of several possible boundary behaviors by which a light wave could behave when it encounters a new medium or an obstacle in its path.
<span>The correct answer is B - Light can travel in a vacuum, and its speed is constant if the source is moving or stationary.</span>