Final answer:
The ultimate source of radon in the environment is the radioactive decay of naturally occurring uranium. Radon is part of the decay chain of uranium-238 and is commonly found in areas with uranium-rich geological formations.
The correct answer is option 1) uranium.
Step-by-step explanation:
The ultimate source of radon in the environment comes from the radioactive decay of naturally occurring uranium. Radon is a radioactive gas that is part of the decay chain of uranium-238. As uranium decays over time, it produces a series of radioactive progeny, including radium, which further decays to form radon.
Since uranium is found in varying amounts in soil and rock formations, radon is also ubiquitous in the environment, particularly in areas with high concentrations of uranium in geological formations.
The correct answer is option 1) uranium.