The electronic configuration of Pt (atomic number 78) is:

Element "E" belongs to the period 4 and group 16 of the periodic table. The valence shell electron configuration of the element, which is just above "E" in the group is

The correct order of increasing ionic radii is

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : The ionic radii of O^2$$-$$ and Mg²⁺ are same.

Reason (R) : Both O^2$$-$$ and Mg²⁺ are isoelectronic species.

In the light of the above statements, choose the correct answer from the options given below.