Option 1: Both by Skin and Lungs – Toads do not rely solely on their skin for breathing during hibernation. While their skin is capable of some gas exchange, it is not sufficient to sustain them during this period.

Option 2: Lungs – While toads do breathe through their lungs during their active periods, they do not rely solely on their lungs for breathing during hibernation. In fact, their breathing rate slows down significantly during this time.

Option 3: Skin – During hibernation, toads primarily rely on their skin for breathing. Their skin is able to absorb small amounts of oxygen from the surrounding environment. This allows them to survive with minimal lung activity.

Option 4: Buccal cavity – The buccal cavity, or mouth, is not involved in the process of breathing during hibernation. Toads do not actively use their mouths for gas exchange during this period.

The correct answer is option 3: Skin.