Fact 1: Amphibians are the first true tetrapods, or vertebrates with four limbs.

Fact 2: Animals with backbones are called vertebrates.

Given the two facts above, answer the question "amphibians are the first true what with four limbs?" with the following options: 
- members of their own species
 - to move people
 - warm-blooded
 - Due to their feet
 - animals with backbones
 - remains of prehistoric life
 - Something to move
 - Generating heat


 

     animals with backbones    