Question

a cell membrane is... the movement of molecules from a high concentration to a low concentration. a rigid wall that prevents anything from moving in or out of a cell. the powerhouse of a cell. a protective barrier that wraps around cells and helps control what moves in and out.

Explanation:

The cell membrane is a protective barrier around the cell. It controls the movement of substances in and out of the cell. The first option describes diffusion. The second option is incorrect as the cell membrane is not rigid and is selectively permeable. The third option refers to mitochondria as the powerhouse of the cell.

Answer:

a protective barrier that wraps around cells and helps control what moves in and out.