Which statement about uranium-235 is true?

• A. It is stable and non-radioactive
• B. It produces no waste
• C. It is unstable and fissionable
• D. It is the only source of all renewable energy

Answer: (C)

Uranium-235 is radioactive and fissile. Its nucleus is unstable, so it decays over long timescales and emits radiation. It can also absorb a slow neutron and undergo fission, splitting into lighter elements and releasing a large amount of energy plus additional neutrons that can continue the reaction. This combination—being unstable and capable of fission when struck by neutrons—is what makes it true to say it is unstable and fissionable.

The other statements don’t fit because uranium-235 is not stable or non-radioactive, and fission produces radioactive waste. It is also not a source of all renewable energy, since renewable energy comes from sources like sunlight, wind, and water, not from nuclear fission.