Fact 1: Lungs are used for breathing air by land animals.

Fact 2: Land Animals Land animals have four limbs.

Given the two facts above, answer the question "Lungs are used for breathing air by animals with what?" with the following options: 
- unidirectional
 - exoskeleton
 - contracting
 - fins
 - four limbs
 - gills
 - kinetic energy
 - eight eyes


 

     four limbs    