Answer:
The correct option is A. Diffusion
Step-by-step explanation:
Diffusion can be described as a mechanism through which molecules move along the concentration gradient i.e from an area of higher concentration to an area of lower concentration. This process does not require energy as the molecules or ions move along the concentration gradient.
Hence, the pumping excess sodium ions by the cell membrane to an area where the concentration of sodium is less would be an example of diffusion.