The correct option is D I, II, III, and IV
Fish use the process known as countercurrent flow, in which water and blood flow in opposite directions across the gills, maximizing the diffusion of oxygen. In the kidney, fluid is flowing along the loop of Henle and exchange takes place between the interstitium and fluid streams moving in opposite directions (descending and ascending) and because osmolality increases progressively with depth in the medulla, the mechanism is termed countercurrent multiplication.The blood vessels in intestinal villi have a countercurrent arrangement of blood flow. The diffusion of oxygen and carbon dioxide in lungs is facilitated by counter current flow in the alveoli.