Nuclear power is generated by:

• A. Fusion of uranium-235
• B. Fission of uranium-235
• C. Chemical reaction of water and uranium
• D. Burning uranium ore

Answer: (B)

The energy in nuclear power comes from fission of a heavy nucleus such as uranium-235. When a U-235 nucleus absorbs a slow neutron, it splits into two smaller nuclei and releases several more neutrons plus a large amount of heat. Those neutrons can then cause additional fissions, creating a controlled chain reaction that continuously releases energy as heat to drive turbines. This is a nuclear process happening at the level of the atomic nucleus, not a chemical reaction.

The other options don’t fit because chemical reactions, like those between water and uranium, release far less energy and involve altering only electrons in atoms, not the nucleus. Burning uranium ore would be chemical combustion, which cannot produce the intense energy density that fission provides. Fusion of uranium-235 would mean merging nuclei, which is not the process used in current light-water reactors.