Which of the following do frogs use for breathing in water?

Frogs use moist skin for breathing in water.
Air is necessary for the survival of all plants and creatures on Earth. Several gases, including oxygen, nitrogen, and carbon dioxide, are mixed to form air. 

Frogs have well-developed lungs, which enable them to breathe in the air when they are on land. In addition, frogs use their moist skin to help them breathe underwater.