Answer: option A) it is stable.
Justification:
Radon (Rn) has atomic number 86. The electron distribution leads to the most stable configuration: the outermost shell (valence shell) is 6s² 6p⁶. That means that it has 8 valence electrons and, therefore, this shell is full. It will not accept more electrons ans will try to keep all of the ones it has.
This is the typical configuration of a noble gas. They are all in the group 18 of the periodic table (the last column). So, as the other noble gases, He, Ne, Ar, Kr, and Xe, Rn is very stable.