Answer: Option (c) is the correct answer.
Step-by-step explanation:
When two small or light atomic nuclei combine together then it results in the formation of a larger nuclei.This process is known as nuclear fusion.
For example,

Whereas when a larger atomic nuclei splits into two small atomic nuclei then it is known as a nuclear fission.
For example,

Thus, we can conclude that the end result of a nuclear fusion reaction is one new atom with a larger nucleus.