Substances that cannot be broken down chemically into other substances are

answer; i believe that the correct answer is(d) nondisjunction during meiosis;

the answer to your question is b

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