The correct answer to the question is : Nuclear fusion.
EXPLANATION:
Nuclear fusion is the thermonuclear reaction in which light unstable nuclei will fuse with each other to form heavy stable nuclei with the release of energy.
This energy is released due to the mass defect.
Photosynthesis, anaerobic respiration are the life processes where gamma rays can not be emitted.
Similarly photoelectric emission results no gamma radiation. In this process, electrons are emitted from the surface of the metal when light of suitable frequency falls on it.
Hence, the correct answer is nuclear fusion where gamma energy is produced due to radioactive process.
