4) the fluid that moves around in the circulatory system of a typical arthropod is a) the digestive juices. b) the intracellular fluid. c) the blood plasma. d) the cytosol. e) the interstitial fluid. e 5) circulatory systems in molluscs a) are open in all species of molluscs. b) are closed in all species of molluscs. c) are open in species of large-sized molluscs and are closed in species of small-sized molluscs. d) are open in species of small-sized molluscs and are closed in species of large-sized molluscs. e) are open or closed without regard to body size. d 6) the circulatory system of bony fishes, rays, and sharks is similar to a) that of birds, with a four-chambered heart. b) the portal systems of mammals, where two capillary beds occur sequentially, without passage of blood through a pumping chamber. c) that of reptiles, with one pumping chamber driving blood flow to a gas-exchange organ, and a different pumping chamber driving blood to the rest of the circulation. d) that of sponges, where gas exchange in all cells occurs directly with the external environment. e) that of humans, where there are four pumping chambers to drive blood flow.