What geological evidence could there be for the presence of an early ocean?
Select one:
a.
Marine sedimentary rocks can be dated back about 4 billion years.
b.
The iron contained in the rocks combined with the oxygen to form reddish iron oxides.
c.
Oxygen is needed to make ozone, a molecule made of three oxygen ions, O3.
d.
No animals would have been able to breathe in Earth's early atmosphere.