Question

About 4 billion years ago, oceans were able to form because _____. cyanobacteria appeared volcanic outgassing helped protect the surface from meteorite bombardment the moon's gravitation cooled the earth the Sun's radiation declined

Answer 1

Because Cyanobacteria appeared

Cyanobacteria's excrement formed a lot of oxygen in the atmosphere which make the earth temperature cold

This allow a liquid water to formed on the surface ( because if the temperature is too high, the water will evaporate) and eventually formed oceans

Answer 2

the answer is "volcanic out-gassing helped protect the surface from meteorite bombardment "