Answer : The correct option is, fission.
Explanation :
Nuclear fusion : It is a process which involves the conversion of two small nuclei to form a heavy nuclei along with release of energy.
Nuclear fission : It is a process which involves the conversion of a heavier nuclei with neutron into two or more small and stable nuclei along with the release of energy.
Decomposition reaction : It is a type of reaction in which a single larger compound decomposes to give two or more smaller molecules as a product.
Combustion reaction : It is a type of reaction in which a hydrocarbon molecule react with the oxygen to give carbon dioxide and water as a product.
When neutrons react with a uranium atom then it produce krypton, barium, and other products with release of energy. So, this reaction is a nuclear fission reaction.
The complete nuclear fission reaction will be:
\(_{92}^{235}\textrm{U}+_0^1\textrm{n}\rightarrow _{56}^{143}Ba+_{36}^{90}Kr+3_0^1\textrm{n}\)
Hence, the correct option is, fission.
