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

Fact 2: Frogs are amphibians and ducks are aves.

Given the two facts above, answer the question "The first true tetrapods, or vertebrates with four limbs include" with the following options: 
- Schwinn
 - frogs
 - Man
 - insects
 - mammals
 - bats
 - Birds
 - feet


 

  frogs       