Answer: D. They fill new roles in the changed environment.
Step-by-step explanation:
Mass extinction is the phenomena of rapidly decrease in the abundance of species from their native land. This is typically caused by catastrophic event like nuclear explosion, tsunami, earthquakes and others. This causes a drastic environmental change.
Some members which are left may play an important role in adapting the change in the environment. They fill up their ecological niches to survive and reproduce this helps in restoring the ecosystem in the changed environment.