Speed = distance ÷ time.
1864/42=44.38
I think it might be the first one: hiv infections. (hope this helps!)
Simple Diffusion Across the Cell (Plasma) Membrane. The structure of the lipid bi-layer allows small, uncharged substances such as oxygen and carbon dioxide, and hydrophobic molecules such as lipids, to pass through the cell membrane, down their concentration gradient, by simple diffusion.
D.lets things enter or exit the cell
