Background radiation includes exposure from which sources?

• A. Natural sources only
• B. Medical imaging
• C. Natural and manmade sources
• D. Nuclear reactor emissions

Answer: (C)

Background radiation comes from two broad categories: natural environmental radiation and human-made radiation. Natural sources include cosmic rays from space, radiation from the Earth's crust (like minerals in rocks and soil), and radon gas that can accumulate in buildings. Human-made sources include medical imaging such as X-rays and CT scans, as well as emissions from the nuclear industry and various consumer products that contribute to exposure. Because background radiation spans both natural and man-made sources, the answer that combines natural and manmade sources is the most accurate. The other options miss either the human-made contributions or only point to a subset of sources (for example, medical imaging or reactor emissions alone).