Where does the oxygen produced in respiration come from

i think the answer would d

bradykinin is a physiologically and pharmacologically active peptide of the kinin group of proteins, consisting of nine amino acids.

the earth is thought to have been formed about 4.6 billion years ago by collisions from a cloud of hydrogen, helium, rock, ice and other materials. these were pulled together by gravity to form objects in and around earth like- asteroids and small early planets called planetesimals.

so, the best possible answer to this question will be option d- to harden materials to form different parts of earth’s layers