Which of the following is an example of an amphibian?

A frog is a prime example of an amphibian because it belongs to a class of animals that typically possess both aquatic and terrestrial adaptations. Amphibians are characterized by their life cycle, which generally involves both an aquatic larval stage and a terrestrial adult stage. Frogs undergo a metamorphic process beginning as eggs, hatching into tadpoles (which are aquatic), and later transforming into adult frogs that can live on land.

In contrast, goldfish are classified as fish, and alligators are reptiles, both of which do not share the distinctive amphibious traits such as skin permeability and a dual life cycle. Salamanders, while also amphibians, specifically are related but are not the only representatives of the group. Therefore, frogs serve as a quintessential example of amphibians, illustrating the lungs and skin adaptations functional for life both in water and on land.