Choose the INCORRECT Statement About the Inert-Pair Effect

Choose the INCORRECT statement about the inert-pair effect.

A) It explains why gallium tends to have the +3 oxidation state but thallium is most often in the +1 state.
B) It can be explained that the bond energies and lattice energies associated with the atoms and ions at the bottom of the groups are not sufficiently large to off-set the ionization energies of the ns² electron.
C) The effect is manifested by ions not losing the outermost pair of electrons.
D) Of the group 14 (4A) metals,only tin exhibits the inert-pair effect.
E) For any group,the inert pair effect is more prominent as the period number increases.