The correct option is D All of the above
Diffusion is a process by which movement of molecules occur from the area of their high concentration to an area of their low concentration. This process continues until along the concentration gradient until an equilibrium is reached.
The diffusing particles, by virtue of their motion, create a pressure called diffusion pressure which is directly proportional to number of diffusing particles.
It is very important to plants as various gases such as oxygen and carbon dioxide move through diffusion.
Hence, all the above statements are true with respect to the process of diffusion.