Opening a Voltage-Gated Channel Generally Involves Which of the Following

Opening a voltage-gated channel generally involves which of the following roles for S6?

A) Forming the ion selectivity filter in combination with S5 and the S5-S6 linker region
B) Sensing transmembrane depolarization via its positively charged amino acids
C) Relieving the physical constraints that block the cytoplasmic mouth of the channel
D) Displacement within in the membrane via interactions with voltage-detecting S4
E) Possibly none: a large body of evidence shows that activation of channel currents can occur independently of an S4-coupled gating mechanism, which casts doubt on the role of S6, too