Decaying uranium atoms in the earth's crust result in Radon gas. Radon gas cannot be synthetically or commercially produced. It is produced as the result of the natural breakdown of uranium i.e. decaying uranium atoms. Radon gas is a naturally occurring radioactive gas. People are exposed to Radon gas via the inhalation and ingestion of the gas. Because it is found in the ground, water or building materials, Radon gas can enter work buildings as well as private dwellings.
I am not entirely sure what you mean by "responding variable" but I'm going to guess it was the vinegar since it has been used as a perservative for years.
Hope that helps in some way.
Answer:
What has a head and a tail but no body?
You can hold it without using your hands or your arms. What is it?
Explanation:
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C. Flood protection is the answer