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
Hello, I don’t see the options
No reaction would occur because copper is more active than silver and silver would be unable to donate electrons to copper.
B. A bond between two atoms: it doesn't matter if it's positive or negative or neutral, if there is a bond between two atoms, it is covalent.
