Biology, Chemistry, physics and calculus.
The answer you pick is right hopefully this helped
I think it's Photosynthesis because photosynthetic bacteria began producing excess oxygen, which added oxygen to the Earth's atmosphere.
Because in DNA there are genes and most of those genes produce proteins.
B) Density (keyword dense) is used to describe something thicker or more filled with. If you make a ball smaller aka decrease its mass and make it thicker aka volume It would make it a lot denser than before