In which of the following classes does respiration take place through gills, lungs, and skin?

 

Concept: The majority of amphibians breathe through their skin and lungs. 
They need their skin to stay wet in order to absorb oxygen, thus they make mucus to keep it moist. 
During their tadpole stage they use gills for breathing as they live in water.
Hence, option B is the correct answer.