Why have amphibian populations declined? 

A)  habitat loss 
B)  pollution 
C)  habitat loss and pollution 
D)  decreased UV radiation

Amphibian populations have declined due to habitat loss and pollution. Habitat loss, such as wetland destruction and deforestation, reduces the available habitat and breeding sites for amphibians. Pollution, such as pesticides and fertilizers, can contaminate their habitats and harm their health. Both of these factors have contributed to the decline of amphibian populations globally. While decreased UV radiation may have an impact on amphibian health, it is not a major factor in the decline of their populations.