Answer:
a. hemoglobin in red blood cells
Explanation:
Carbon dioxide is constantly produced by cells during cellular metabolism (cellular respiration), generating a concentration difference between the interior of the cell and its exterior (intercellular or interstitial space), and a consequent diffusion of this carbon dioxide into the interstitial fluid. Interstitial fluid now has a higher concentration of carbon dioxide than blood plasma, which causes a diffusion into the capillary. Carbon dioxide is carried by hemoglobin or dissolved in plasma.
