Correct order of ionic radii:
\(O^{–2} > Mg^{+2}\)
This is because among isoelectronic species, the size of anions are greater than the size of cations.
Statement (II) is correct as both \(O^{–2}\) and \(Mg^{+2}\) are isoelectronic.
Hence, the correct option is (D): (A) is false but (R) is true.
Match List-I with List-II: List-I