Global warming is a concern because
$a$. the rate of change in climate is projected to be faster than the rate at which many species can shift their ranges.
$b$. it is already too hot in the tropics.
$c .$ climates have been so stable for thousands of years that many species lack the ability to tolerate variable temperatures.
$d$. climate change will be especially harmful to rare species.
$e .$ None of the above