Final answer:
c) Diffusion. The process of moving substances from low concentration to high concentration using energy is called active transport.
Step-by-step explanation:
When chemical substances are moved from a region of low concentration to a region that is already high in concentration, the process is known as active transport. This is a type of transport where proteins within the cell membrane act as 'pumps', using cellular energy, typically in the form of ATP, to move substances against their concentration gradient, from lower to higher concentration.
Diffusion is the movement of molecules from an area of high concentration to an area of low concentration. It is a passive process that occurs until the concentration is equal across a space. In this case, the process described in the question is diffusion (c).