Carbon dioxide moves through the plasma membrane through the process of A. osmosis
B. active transport
C. diffusion
D. facilitated diffusion
E. both diffusion and osmosis​

As oxygen-rich (and carbon dioxide-poor) blood travels by a cell the oxygen diffuses through the cell membrane to the area of lower concentration inside the cell. It can do this easily because the oxygen molecule (O2) is very small and has no charge or polarity. The oxygen is used up rapidly by mitochondria. This rapid consumption causes oxygen to constantly move into the cell from the blood. Therefore the answer is C