Species Able to Recolonize the Mount St

Species able to recolonize the Mount St.Helens area after the volcanic eruption in 1980 had to pass through several "filters" to become established in the ravaged area.What was the most immediate requirement of these species before they could become established?

A) They had to withstand environmental conditions in the area.
B) They had to successfully interact with other species already in the area.
C) They had to be part of the regional species pool surrounding the area.
D) They had to build up large enough populations to remain viable.
E) They had to be able to leave the area in case of another eruption.