Mass of H2C2O4 :
mm = 90.04 g/mol
number of moles : 0.0223 moles
m = n * mm
m = 0.0223 * 90.04
m = 2.007 g
hope this helps!.
B.
The cynobacteria were already there without the oxygen, so that rules out A, and a lot of prokaryotes were anaerobic, so that rules out C. Finally, Photosynthesis does not require oxygen. Instead, Oxygen is a waste product of it. Therefore, it cannot be D. So, we are only left with B
Hoped this helped :D
