Which processes can occur without using ATP directly?

The processes that can occur without using ATP directly include both simple diffusion and facilitated diffusion, making the correct answer C, as these mechanisms rely on concentration gradients rather than direct energy expenditure.

Simple diffusion is a passive transport process where molecules move from an area of high concentration to an area of low concentration until equilibrium is reached. This movement does not require energy in the form of ATP because it is driven solely by the natural tendency of molecules to disperse in space.

Facilitated diffusion, while involving specific transport proteins, also occurs along a concentration gradient and similarly does not require ATP. The proteins help transport larger or polar molecules that cannot easily cross the lipid bilayer, but the process remains passive as it relies on existing concentration differences rather than requiring energy input.

Choosing the correct option recognizes that both processes leverage the inherent kinetic energy of molecules instead of breaking down ATP for energy.