CONCEPT: Binding Energy of the nucleus: The energy that holds a nucleus together. or the energy required to disassemble a nucleus into its constituent protons and neutrons completely is called binding energy. or the energy that would be liberated by combining individual protons and neutrons into a single nucleus is called binding energy. The total binding energy of an element is the product of binding energy per nucleon and mass number. If in a reaction total binding energy of the resultant products is more than the total binding energy of the reactant products then in the reaction energy is absorbed and similarly vice-versa. CALCULATION: Total binding energy of A = EA = 5 × 30 = 150 MeV Total binding energy of B = EB = 8.5 × 60 = 510 MeV Total binding energy of C = EC = 8 × 90 = 720 MeV Total binding energy of D = ED = 7 × 120 = 840 MeV Calculation of final and initial energies of elements for each of the reactions. Reaction (a) D → 2 B 2EB - ED = 2(510) - 840 = 180 MeV 180 > 0 So energy is absorbed in this reaction. Reaction (b) C → B + A EB + EA - EC = 510 + 150 - 720 = -60 MeV -60 So energy is released in this reaction. Reaction (c) B → 2 A 2EA - EB = 2(150) - 510 = -210 MeV -210 So energy is released in this reaction. So energy is released in (b) and (c) reaction. So the correct answer is option 2.