Which of the following traits is not a characteristic of amphibians?

During hibernation, frogs respire through the gills.

The correct answer is Option (4) - During hibernation, frogs respire through the gills.

Amphibians are those animals who are found both on land & water i.e. amphibians can live in aquatic as well as terrestrial habitats. 
In Amphibians, respiration takes place through the gill, skin, and lungs.During hibernation, frogs respire through the skin. They have porous skin that requires moisture. ie the amphibian skin is moist (without scales).  They have three-chambered hearts, two auricles, and one ventricle.

Frogs have two transparent eyelids, one on the bottom, one on the top, and a third semi-transparent eyelid called the nictitating membrane. Amphibians’ eyes have eyelids.The body of Amphibians is divided into the head and trunk.
In amphibians, a tympanum is located just behind the eye but it does not process sound waves; it simply transmits them to the inner parts of the amphibians ear which are protected from the entry of water and other foreign objects.

The tympanum is a large external oval-shaped membrane made up of non-glandular skin. They are cold-blooded. Examples of Amphibians are Frog, Necturus, Salamander, etc.