Plant T is placed beside a sealed gamma source, and the source is then removed. Plant U is watered with water containing radioactive atoms, and the watering is then stopped. Plant U receives no more radioactive material after this.
Which statement correctly describes the two plants one hour later?
Plant T continues to emit gamma radiation absorbed from the source; the radioactive atoms in plant U continue to decay.
Plant T is no longer exposed and has not become radioactive; radioactive material in plant U continues to decay.
Plant T has radioactive material deposited by the gamma rays; the radioactive atoms in plant U stop decaying inside the plant.
Plant T is no longer exposed and has not become radioactive; plant U stopped emitting radiation when the watering stopped.