Answer: The correct answer is option (a).
Step-by-step explanation:
Nuclear fission and nuclear fusion both are types of nuclear reactions.
In nuclear fission , splitting of a large atom into smaller atom takes place with release of energy in large amount.
In nuclear fusion , two small atoms combine with each other to form a large atom with release in energy in large amount
The energy released in both the nuclear fission and fusion is termed as nuclear energy.
Hence, the correct answer is option (a).