Fact 1: Skin is used for breathing air by frogs.

Fact 2: Frogs breathe with their lungs and skin.

Given the two facts above, answer the question "What do frogs breathe with their lungs?" with the following options: 
- gas
 - CO 2
 - fossil fuels
 - air
 - nose
 - O2
 - water
 - CO2


 

    air     