The best answer is C.
The outermost covering of plant cells is called the cell wall. It is made up cellulose, is rigid and can be seen under a light microscope. It is absent in animal cells.
The outermost covering in animal cells is the cell membrane. It is made up of lipids, proteins, and small amounts of carbohydrates. It is a thin and delicate structure that can only be seen under an electron microscope.
Plant cells have both cell wall and cell membrane