Answer:
I am not sure but I think the answer is of first one.
There are 6 molecules of O2.
"O2" is the formula for one molecule oxygen, which has 2 atoms.
The subscript (small) "2" tells you how many atoms are in the molecule.
The coefficient is the big number tells you the number of molecules.
In 6O2, there are 12 atoms in total (6 molecules of 2 atoms each).
It is the Archean Eon! :)
