This doesn’t fit, because we have no reason to think there’s “always a possibility plate velocity could increase.” The author never suggested anything that implies plate velocity can always increase. Since (A) isn’t supported, it wouldn’t be a logical completion.

This doesn’t fit, because it’s unsupported. The author never suggests that lower levels of subduction imply higher chance of shallow subduction angles. The author never presents a correlation between amount of subduction and angle of subduction.

This doesn’t fit, because the author’s emphasis at the end is on the “nature of the subduction” taking place — the direction of the plates that collide. The author doesn’t suggest that subduction might always increase and that this is why there might be risk in low subduction zones.

This doesn’t fit, because it’s not supported. The author doesn’t suggest that subduction at low levels “inevitably” (always) results in a lot of seismic activity. The angle of subduction matters.

This fits at the end, because this helps explain why regions with low levels of subduction may be at risk of earthquakes. If a plate in a collision descends at a shallow angle — meaning, the plates collide in opposite directions — then there’s a lot of earthquake-producing friction that results.