The process of keeping the internal environment of the body stable by responding to changes in the external environment is known as homeostasis. Which of the following accurately describes a mechanism for maintaining homeostasis at the cellular level?

Passive transport, where ATP is used to facilitate the movement of molecules from
high to low concentrations.

Facilitated transport, where enzymes are used to increase the rate of solvent transfer
across a membrane.

Active transport, where the solution is pumped across a membrane to from high to
low concentrations.

Active transport, where molecules are pumped across the cell membrane against the
gradient from low to high concentration.