Light does not travel at a constant speed in a vacuum, compared to in air, because the light is being absorbed by atoms and molecules in the air. But light does travel at a constant speed in a vacuum.
So I agree with A
All that talk about moving forward is irrelevant (I think)
Unless you're able to provide a diagram representing the problem, there's not much I can do so solve this problem.
Answer:
c- dry cells can not be recharged
~The picture below shall help :)
-Hope this helped ^_^