Option (d) is correct.Fission and fusion convert nuclear energy to both radiant and thermal energy.
fission is a process in which bigger nucleus breaks into two or more smaller nuclei with the liberation of a large amount of energy.
Fusion is a process in which two small nuclei fuse together to from an intermediate size nucleus with the liberation of tremendous amount of energy
During fission and fusion, energy is released in the form of both light (radiation) and heat.we can then convert that energy into useful form.