The frog has three respiratory surfaces on its body that it uses to exchange gas with the surroundings: the skin, in the lungs and on the lining of the mouth. While completely submerged all of the frog's respiration takes place through the skin.
In most fish respiration takes place through gills. Whale, dolphin and Lungfish, however, possess one or two lungs. The labyrinth fish have developed a special organ that allows them to take advantage of the oxygen of the air, but is not a true lung.
Leech and earthworm breathe through a gas exchange through their skin. This occurs using areas of the body cavity known as capillary beds. Gas exchange occurs between the capillary beds of the body surface and the environment. Oxygen is carried by the respiratory pigment hemoglobin, which is dissolved in the fluid portion of the blood.
Answer : (d)