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

Fact 2: For example, the frog is covered with skin that is porous to air.

Given the two facts above, answer the question "Frogs breathe through their skin, which is what?" with the following options: 
- poured
 - filtered
 - fibrous
 - warm
 - unique
 - evolving
 - porous
 - fermented


 

       porous  