In Voltage-Activated Channels, Preferential Ion Selectivity for Calcium Over Sodium

In voltage-activated channels, preferential ion selectivity for calcium over sodium is governed by which of these factors?

A) Cumulative negative charge of amino acids that line the pore
B) An ensemble mix of negative, positive, and neutral amino acids that line the pore
C) Glutamine residues at four positions that line the pore
D) Aspartate followed by glutamate-that pattern repeated twice-at four key positions that line the pore
E) Characteristic features of the P-loop