The statement which is not true is : D. All natural radiation is at a level low enough to be safe.
Explanation:
Natural radiation also called background radiation is all around us,in our environment.A good example is that from cosmic radiations from the sun and the galaxy.High radiations can also originate from mineral deposits such as uranium in the soil or rocks, which could harm a person exposed to it.
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Nuclear radiations :https://brainly.com/question/2479177
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