Which of the following processes does NOT require energy?

Facilitated diffusion is a process that allows substances to move across a cell membrane with the aid of transport proteins. It is driven by the concentration gradient of the molecules involved, which means that substances move from an area of higher concentration to an area of lower concentration. This gradient provides the necessary energy for the movement, which is inherent in the system and does not require additional energy input from the cell, such as ATP. As a result, facilitated diffusion is considered a passive transport mechanism.

In contrast, processes like endocytosis, active transport, and exocytosis involve the movement of substances against their concentration gradient or the bulk transport of materials, which necessitates energy expenditure from the cell.