Which statement describes the energy involved in diffusion? Diffusion requires energy in all cases. Diffusion requires energy only to move material in through the cell membrane. Diffusion does not require energy in any situation. Diffusion requires energy only to move material out through the cell membrane.

Both b and d can be correct

Explanation:

Generally, diffusion does not require energy (making option a wrong) because it is the movement of particles from a region of high concentration to a region of low concentration hence diffusion moves particles in the direction of a concentration gradient. An example of this is the passive transport (for instance, uptake of glucose by a liver cell).

However, in some cases, when diffusion is against the concentration gradient (i.e when particles move from a region of low concentration to a region of high concentration), diffusion will require energy in a case like this (making option c wrong). An example of this is active transport (transport of protein called sodium-potassium pump which involves pumping of potassium into the cell and sodium out of the cell).

The explanation above shows that diffusion can require energy to move particles (in or out) of the cell through the cell membrane.