Coal-fired plants put coal through a combustion reaction, in order to generate heat energy. While nuclear plants use principals of fission to generate power.
A combustion reaction does not split an atom, while fission is the process of breaking apart atoms, so we can conclude hat it isn’t #1.
I don’t think humans have even been able to reliably fuse atoms together, thus #2 can not be correct.
Fission is not a chemical reaction, therefore it can’t be #4.
I think both provide heat which then heats water thus turning a turbine that generates electricity. #3 is deductively the correct answer.