I believe the correct answer from the choices listed above is the third option. It is oxygen that is a necessary reactant for cellular respiration to occur. Cellular respiration, in a sense, is breaking down sugar in the presence of oxygen. Hope this answers the question.
Some bacteria breathe with oxygen, but others use forms of respiration. But, bacteria don't breathe in the same way humans do.
All engineers solve problems related to any field. so the answer is option A.
Hope it helps!!!
Offset sexual reproductions
