Which statement accurately describes the difference between fission and fusion?

• A. Fission splits atomic nuclei
• B. Fusion splits atomic nuclei
• C. Both processes release energy by splitting atoms
• D. Fission splits atomic nuclei; Fusion combines nuclei

Answer: (D)

The main idea here is that nuclear energy comes from changes in binding energy, and the two processes differ in what they do to the nuclei. Fission breaks a heavy nucleus into smaller nuclei, releasing energy because the resulting fragments have a higher average binding energy per nucleon than the original heavy nucleus. Fusion, by contrast, combines light nuclei to form a heavier nucleus, releasing energy when the new nucleus has a higher binding energy per nucleon than the starting light nuclei.

That’s why the statement that fission splits atomic nuclei and fusion combines nuclei is the best description. It correctly identifies the key difference in the actions of the two processes. The other options are misleading: fusion does not split nuclei, and saying both processes involve splitting atoms ignores the fusion side, which involves merging nuclei (and releases energy for that reason).