From about 4 billion years ago to about 2.5 billion years ago, oxygen gas became more common in Earth's atmosphere. Oxygen was a toxic compound to most life forms from that time period. Today, oxygen is required by all but some of the most primitive life forms. Which statement best explains how early life forms that were harmed by oxygen evolved into today's life forms that require it?
Warming temperatures allowed the colonization of land environments, where oxygen was more plentiful.
Carbon dioxide-using species all became extinct, which allowed oxygen-using life forms to flourish in shallow oceans.
Over time, many species gradually adapted to a more oxygen-rich environment, allowing them to survive in shallow water and on land.
The growth of seas allowed early species to survive by using dissolved carbon dioxide in seawater rather than using it directly from the air.