Why Do Conservation Biologists Believe That Global Warming May Lead

Why do conservation biologists believe that global warming may lead to extensive decimation of species?

A) Because little change in plant community composition has occurred in the past, we cannot expect present communities to adapt to climate change.
B) The magnitude of climate change will be much greater than past periods of climatic change.
C) Many sedentary species may not be able to shift their ranges at the same pace as the northern movement of temperature zones.
D) Both b and c
E) All of the above