In useful fusion, smaller nuclei fuse together into larger nuclei and also produce : black hole entropy

energy from vacuum fluctuations

energy from excess mass

free quarks

energy from excess mass

Explanation:

The correct answer for the given question out of the given options is the option " energy from excess mass ".

This happens due to the fact that some of the matter is converted into the energy during the fusion of atoms.

The relation that can be stated is E = mc²

where,

E is the energy

c is the speed of the light

m is the mass of the matter