Correct Option: D

Special theory of relativity postulates that the speed of light is a universal constant. We cannot reach speeds greater than the speed of light by the relativistic addition of velocities. The equation is how to reconcile with this result of special relativity with Newton’s second law, F=ma. It would be seen that any constant force, no matter how small, applied for a considerably very long time, should continuously accelerate any mass ‘m’ at a rate a=f/m until the speed was arbitrarily very large. Einstein, concluded that energy has inertia i.e. the more energy a body possess, the more inertia that body will display. Since, inertia is a property of matter, which is associated with mass. Thus from Einstein’s argument mass is simply a property attributed to the total energy of the body and only the total energy is required, to know the total mass of the body.