What Is the Probable Origin of the Electrical Conductivity of Cadmium

What is the probable origin of the electrical conductivity of cadmium when its electron configuration is [Kr]4d ¹⁰5s²?

A) One electron on each atom is promoted to a 5p orbital when many cadmium atoms interact, and the electrons are free to move.
B) Empty 5p orbitals can be combined to form a conduction band that overlaps the valence band, and electrons that move from the valence band to the conduction band are mobile.
C) Pairs of mobile electrons form when many cadmium atoms interact.
D) Cadmium has a very low ionization energy, which makes the valence electrons highly mobile.
E) 4d orbitals mix with 5s orbitals, creating empty energy bands in which electrons can move.