I think that it's cannot include supernatural explanations, or C.
If i got it wrong sorry
The correct option is STRONTIUM.
Strontium is a group 2 element, that means it has two electrons in its outermost shell. This element will prefer to lose these two electrons in its outermost shell in order to attain the octet form, therefore, it will form electrovalent bond with non metals which it can donate two electrons to.
C) Tc-99 is a radioactive isotope also known as radioisoptope.
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Answer : Option 4) Region of the most probable electron location.
Explanation : As per the electron cloud model of the atom, an orbital is a region where the probability of finding an electron is highest. According to this model which was used to identify the probable location of the electrons when they go around the nucleus of an atom.
This electron cloud model was different from the older Bohr atomic model by Niels Bohr.