How molecular oxygen is important for all oxygenated animals?

[A]: The evolution of molecular oxygen is concerned with photosystem-1 (PS-I). [R]: The photosystem-11 (PS-II) is not involved in the evolution of oxygen

Gram molecular volume of oxygen at STP is

how many molecules of oxygen are bound to one molecule of haemoglobin

Oxygenic photosynthesis occurs in

How is oxygen prepared in the laboratory?