Question

How is modern Earth different from Earth over four billion years ago?

Constantly bombarded with comets and asteroids
Little to no oxygen
High levels of ultraviolet radiation
Protective atmosphere

Answer 1

Answer: little to no oxygen

Explanation:

Answer 2

Early earth had low oxygen, UV radiation, high heat, not a lot of water. Modern earth has lots of oxygen, low UV radiation, abundant amount of water, ozone layer.