Fact 1: Amphibians have permeable skin that easily absorbs substances from the environment. Fact 2: All frogs are amphibians. Given the two facts above, what feature allows frogs to absorb substances from the environment?

OPTIONS: 1. four limbs. 2. poison dart frog. 3. hydrate their cells. 4. permeable skin. 5. layers of fat. 6. a cuticle. 7. predators. 8. double eyelid.
The answer is:
4.