When does menstration occur

Starts at ages 8-16. Occurs every month for 2-9 days, typically a 28-30 day cycle.

Explanation:

Not needed

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

i believe the answer would be b. hope it : )