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.