How many years to double between 2 billion and 4 billion?

2 billion

Explanation:

Because 2 billion plus 2 billion is 4 billion hope this helps :)

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

the answer is c.

by: nicholas dooley