What are the long strands of DNA called?

A. Chromosomes
B. Fossils
C. Genes
D. Mutations

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

which fault and or fold did you find most difficult to diagram