Which of the following groups is more vulnerable to extinction than the other three? 

Among vertebrates, amphibians are most vulnerable for extinction with 32% species facing the threat of extinction. Amphibians are dependent on clean fresh water and damp habitats and are considered vulnerable to habitat loss (deforestation), changes in water or soil quality and the potential impacts of climate change, and in addition many species are suffering from an epidemic caused by a chytrid fungus.