Which of these is true of a cell membrane? A: A cell membrane has a property called selective judgment. B: A cell membrane blocks all particles from coming through. C: A cell membrane is a protective structure that encloses a cell. D: all of the above

Flock x flock y flock z total pieces of food eaten (from previous page) 147 93 60 food percentage* % % % simulated number of birds in flock for 3rd generation** * divide each flock's total pieces of food by 300, the total number of pieces of food eaten. ** multiply the food percentage for each flock by the total number of birds (30).