Final answer:
Uranium is the concentrated uranium oxide used as the raw material for commercial nuclear fuel.
Step-by-step explanation:
The concentrated uranium oxide used as the raw material for commercial nuclear fuel is Uranium (Option B).
In a nuclear reactor, uranium-235 undergoes fission, releasing a large amount of energy. The percentage of uranium-235 in naturally occurring uranium is less than 1%, so the uranium ore must be enriched to increase the concentration of uranium-235 to about 3%. This enriched uranium is then formed into fuel rods for use in nuclear power plants.
Plutonium is also used as a nuclear fuel, but it is not the concentrated uranium oxide used as raw material.