Statement (i): The mass energy of a nucleus is actually smaller than the sum of the mass energies of individual protons and neutrons due to the binding energy. Therefore, this statement is false.
Statement (ii): When a nucleus is separated into its nucleons, energy equal to the binding energy must be supplied to overcome the nuclear forces holding the nucleons together. This statement is true.
Statement (iii): The binding energy is indeed a measure of how strongly the nucleons (protons and neutrons) are held together within the nucleus. This statement is true.
Statement (iv): Nuclear fission involves the splitting of a heavy nucleus into lighter nuclei, which results in a release of binding energy, leading to a higher binding energy per nucleon in the fragments. This statement is true.
Thus, the correct answer is that statements (ii), (iii), and (iv) are true.