Which is the best definition of a cellular membrane?

the cladogram shown here shows similarities and differences among several classes of vertebrates. anatomically, the four have limb structure as their common ancestor. we might separate the mammals from the other three classes because they a) divergent; do not lay eggs b) identical; are warm-blooded c) varied; a four chambered heart d) homologous; have mammary glands

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.