As described in Investigating Life 20.1, scientists found that the range of the alpine chipmunk has shifted about 500 meters up in elevation, leading to isolated subpopulations on individual mountaintops. According to the researchers, what has caused this shift?
A.harmful UV radiation due to the ozone holeB.habitat destruction due to acid precipitationC.introduction of nonnative speciesD.climate warming due to increased CO2 concentrations