* A. found in all organisms: This is incorrect. Cell walls are found in plants, bacteria, fungi, and some protists, but not in animal cells.

* B. composed of a lipid bilayer: This is incorrect. Cell walls are primarily composed of carbohydrates (like cellulose in plants) and other structural polymers. The cell membrane, on the other hand, is composed of a lipid bilayer.

* C. flexible barrier: This is incorrect. While the cell membrane is flexible, cell walls provide a rigid and supportive structure.

* D. made tough fibers: This is correct. Cell walls are made of tough, rigid fibers that provide structural support and protection to the cell.

In summary: Cell walls are distinct from cell membranes in their composition, structure, and function.