Why Might Small Group Societies Generally Ostracize Individuals for Short

Why might small group societies generally ostracize individuals for short periods of time rather than completely expel them as a form of punishment?

A) The expelled individual may join a competing group.
B) The expelled individual may seek revenge against the group through violence.
C) It would mean certain death for the individual expelled and would weaken the group.
D) It often results in the expelled individual forming his or her own rival group to compete for resources.