Water (H2O), Carbon Dioxide (CO2), And Oxygen (O2) Are All

Water (H2O), carbon dioxide (CO2), and oxygen (O2) are all quite small molecules, yet they move across cell membranes differently. Both CO2 and O2 passively diffuse across the cell membrane directly while H2O moves across the cell membrane by facilitated diffusion. What can be concluded about these three molecules based on the way they react to the cell membrane?