Fact 1: Skin is used for breathing air by frogs. Fact 2: Frogs breathe with their lungs and skin. Given the two facts above, what do frogs breathe with their lungs?
Available choices:
[1]. gas
[2]. CO 2
[3]. fossil fuels
[4]. air
[5]. nose
[6]. O2
[7]. water
[8]. CO2
[4].