Final answer:
The correct option is 4) active transport. Active transport refers to the movement of a substance across a cell membrane going from an area of lower concentration to an area of higher concentration, against the concentration gradient. This process is used to move particles from a region of lesser concentration to a region of greater concentration.
Step-by-step explanation:
The correct option is 4) active transport.
Active transport refers to the movement of a substance across a cell membrane going from an area of lower concentration to an area of higher concentration, against the concentration gradient. In this type of transport, proteins within the cell membrane act as "pumps," using cellular energy (ATP) to move the substance. This process is used to move particles from a region of lesser concentration to a region of greater concentration.