A. the theory of special relativity is the correct answer.
Explanation:
The theory of special relativity was first proposed by Albert Einstein.
Albert Einstein his Special theory of relativity determined that the speed of light inside the vacuum is the same irrespective of the speed at which the observer sees.
The theory of special relativity explains that the speed of light remains the same for all the non accelerating observers and describes that the mass can be changed into energy and energy can be changed into a mass.
