What is the correct answer?
Body covered with dry and cornified skin, scales over the body are epidermal, they do not have external ears.
Body is covered with moist skin and is devoid of scales, the ear is represented by a tympanum, alimentary canal, urinary and reproductive tracts open into a common cloaca.
Fresh water animals with bony endoskeleton and airbladder regulate buoyancy.
Marine animals with cartilaginous endoskeleton and body is covered with placoid scales.