What gas dominated earth’s first atmosphere? water vapor

hydrogen

methane

nitrogen

hydrogen gas dominated earth's first atmosphere?

it's anything that aren't producers and consumers.

explanation:

you've got to be clear on what "this" is

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