The correct answer is number 5) at the nuclear reactor site.
Most of the high-level waste stored in the United States is at the nuclear reactor site.
Just people who specialize in the radioactive waste can handle this risky procedure because high-level radioactive waste needs treatment by the experts to truly isolated from the biosphere. Radioactive plants keep the waste deep underground because nobody wants another accident like the one that happened in Chernobyl on April 26, 1986.
The other options of the question were 1) the ocean. 2) mountain peaks. 3) volcanic fissures. 4) salt mines.
