Short Videos by Experts' Global - GMAT Shots | Verbal

Fusion, the process through which the sun produces heat and light, has been studied by scientists, some of whom have attempted to mimic the process in their laboratories by blasting a container of liquid solvent with strong ultrasonic vibrations.

(A) Fusion, the process through which the sun produces heat and light, has been studied by scientists,
(B) Fusion, the heat and light produced by the sun, has been studied by scientists,
(C) Fusion, the process through which heat and light are produced by the sun, has been studied by scientists,
(D) Scientists have studied fusion, the process the sun uses to produce heat and light,
(E) Scientists have studied fusion, the process the sun uses to produce heat and light, and

As per the explanation given in video,
from above question if we see the statement between the 2 commas i.e the process through which the sun produces heat and light, has been studied by scientists
this info. should be non essential.then how come Option "A" can be the correct answer for.
because if we remove infomation between commas, then " fusion some of whom...." does not make any sense.

I am bit confused about it, can some one please explain me this.