You are presented with the quiz "amphibians are the first true what with four limbs?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "amphibians are the first true tetrapods, or vertebrates with four limbs" and "animals with backbones are called vertebrates". 

So, what's the best answer to the question?


 

     animals with backbones      