Scientists have arranged all of the different types of material or elements we can find into groups known as what?

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

just finished the test, the answer is d, greg is the least cost-effective because he charges the most for the project