The study of a chemical is called chemistry.
The correct answer is A
Radioactive decay is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive.
The radioactive of the Ra is option A that is:-
[tex]RA^{226}_{88}----->Rn^{222}_{86} +He^4_2[/tex].
During the decomposition, the element is breakdown into the neutron, proton, and electron.
Hence, the correct answer is A.
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