HEY THERE !!
It is called SUBLIMATION.
so the correct answer is (D).
<span>Two plastic balls suspended by strings are placed close to each other. If they have the same charge then they will repel each other.</span>
The rest energy of a particle is

where

is the rest mass of the particle and c is the speed of light.
The total energy of a relativistic particle is

where v is the speed of the particle.
We want the total energy of the particle to be twice its rest energy, so that

which means:


From which we find the ratio between the speed of the particle v and the speed of light c:

So, the particle should travel at 0.87c in order to have its total energy equal to twice its rest energy.