Answer:
Step-by-step explanation:
Nuclear Fission -
The process of the splitting of atom , by radioactive decay process or by any collisional impact .
Sun contains many radioactive isotopes like , thorium , uranium , etc .
The nuclear fission process is an intrinsic property of the radioactive nuclides.
Nuclear Fusion -
The process , where two or more than two atomic nuclei combines to form one or more different atomic nuclei and subatomic particles .
The energy released in both the process is almost same ,
But on the surface of Sun , hydrogen is abundantly present , hence , hydrogen fusion is possible , so the dominant source of energy on the sun is Fusion .