Which of the following is true of active transport? a In active transport, the cell does not have to do any work as nature moves the materials across the cell membrane.
b The energy used by the cell is in the form of the ADP molecule.
c Molecules called pumps function to control active transport.
d In active transport, the cell must push or pump the molecules from areas of high concentration to areas of low concentration.

Some cells function best at a pH of 5, while others are better at pH 7. ... Cell membranes are semipermeable, meaning they have control over what molecules can ... We call this evening-out moving “downhill”, and it doesn't require energy. ... Transport that directly uses ATP for energy is considered primary active transport.

Explanation:

answer; ///(b) it is composed of four protein chains and four heme groups;

gold i'm pretty sure i might be wrong