Which of the following pairs of atoms shows inert pair effect?

Some of the heavier elements/atoms, which are having three or four electrons in the outermost shell are expected to form di, tri or tetravalent ions, but sometimes they do not lose electrons and hence, form cations with lower positive charge. Such electrons which do not participate in ion formation are called inert parts. This effect is known as inert pair effect. Probably, this effect takes place when n = 4 or > 4 only. Sn (Z = 50) = [Kr] 4d¹⁰, 5s², 5p² Sn²⁺ = [Kr] 5d¹⁰, 5s², 5p⁰ Pb (Z = 82) = [Xe] 5d¹⁰, 6s², 6p² In Sn²⁺, 5s² is an inert pair which does not take part in ion formation. Pb²⁺ = [Kr] 5d¹⁰, 6s², 6p⁰ In Pb²⁺, 6s² is an inert pair which does not take part in ion formation.