Na nuclear reaction, mass must be lost to produce energy. true or false

The answer is true. Nuclear reactions, unlike chemical reactions, do not explicitly follow the law of conservation of mass in the sense that part of the mass is lost in nuclear reactions. In nuclear reactions, some of the mass is actually converted to energy. This is made possible due to Einstein's equation: E = mc^2. Also, nuclear reactions make use of nucleons which give off greater energies than chemical reactions.