Which one of the following is not a natural source of radiation exposure?

The correct response identifies nuclear power plants as not being a natural source of radiation exposure. Natural sources of radiation primarily come from the environment and include elements that occur naturally in the earth, the atmosphere, and living organisms.

Radioactive minerals are indeed a natural source as they are found in the earth’s crust and emit radiation due to the decay of unstable isotopes. Cosmic radiation refers to high-energy particles that originate from outer space and interact with the Earth's atmosphere, making it another natural source of radiation exposure. Plants can also contribute to radiation exposure through the uptake of radioactive isotopes from the soil, making them a natural source as well.

In contrast, nuclear power plants are man-made facilities that generate electricity through nuclear reactions, specifically the fission of uranium or other radioactive materials. The radiation associated with nuclear power plants is a result of human activity and technological processes rather than a natural occurrence. Therefore, recognizing nuclear power plants as a non-natural source of radiation exposure is essential for understanding different radiation sources and their origins.