Answer: The correct option is, 2.
Explanation:
Nuclear fission: It is defined as the reactions in which a larger unstable nuclei breaks into two or more smaller stable nuclei.
Nuclear fusion: It is defined as the reaction where two smaller nuclei combine together to form a larger nuclei.
Option 1 & option 2 shows fusion reaction and option 3 & option 4 shows fission reaction.
In option 1, helium itself is forming but in option 2, element is heavier than forming which is, neon.
Hence, the correct option is 2.
