Which of the following are sources of radiation?

The answer encompasses all possible sources of radiation. Natural background radiation is a constant, omnipresent source that includes cosmic radiation from outer space, and terrestrial radiation from naturally occurring radioactive materials in the Earth's crust.

Radioactive fallout from nuclear testing represents a significant anthropogenic source of radiation exposure, resulting from the dispersal of radioactive materials in the atmosphere during nuclear explosions.

Radiation from medical diagnosis is another important source, where various diagnostic procedures utilize ionizing radiation, such as X-rays or CT scans, to provide critical health information.

By recognizing all these sources collectively, the answer captures the full scope of radiation exposure that individuals may encounter in both natural and medically related contexts, illustrating the diverse origins of radiation in our environment.