Which homeostatic process moves particles against a concentration gradient?
a. dynamic equilibrium
b. passive transport
c. osmosis
d. active transport

An active transport is the process by which a substance is transported or transferred from one area to another using a chemical energy in the course. 

As oppose to passive transport, active transport’s key to its description uses energy to be able to transfer the said substance. This is important in a lot of aspects such as providing the needed elements or compounds in cellular activity.