Why Do Experts Think That Protected Areas,even Though They Have

Why do experts think that protected areas,even though they have been successful in the past,are not a long-term solution for endangered species?

A) There are not enough nature preserves,which have the highest level of protection.
B) Populations within these areas will become inbred after a while,which decreases the genetic diversity and makes the population more vulnerable to disturbances.
C) The areas themselves are being degraded due to factors like global warming and human construction,so the populations within the areas have to go outside of them,in unprotected areas,to find suitable habitats.
D) There is not enough species diversity within these areas.
E) Experts actually think that these kinds of protected areas are the solution for long-term management of endangered species.