Inhaled radionuclides are not likely to be released from which of the following sources?

A. the sun

B. medical facilities

C. industrial waste facilities

D. terrestrial areas where nuclear weapons testing and accidents occurred

Inhaled radionuclides are not likely to be released from the sun. The answer is letter A. Medical facilities, industrial waste facilities and other terrestrial areas where nuclear weapons testing and accidents occurred contains radionuclides. Radionuclides are essential in these types of facilities because of their function.