Why Are Species with Rapidly Shrinking Populations Especially Vulnerable to Extinction

Why are species with rapidly shrinking populations especially vulnerable to extinction?

A) Reductions in population size can lead to genetic drift and loss of genetic variation.
B) Populations reduced to a small size or confined to a small range can easily be eliminated by local disturbances.
C) Species with specialized habitat or dietary requirements are less likely to become extinct than species with more generalized requirements.
D) Both a and b
E) All of the above