We learned in the last unit about the three different types of cells, animal, plant, and bacterial cells. Which statement below is correct concerning these cells and the cell membrane? (a)The cell membrane is the outer boundary of the cell that has pores in it to allow materials in and out.

(b)If all cells did not have cell membranes, they could not maintain homeostasis to obtain nutrients and make energy to grow, remove wastes, reproduce, and live.

(c)The cell membrane of a cell is impermeable to pathogens that try to invade just like a castle keeps out invading armies.

(d)All cells don't have to have cell membranes if they have cell walls to protect them. Cell walls are quite strong and stiff.