<span>The answer is (1) releases energy. In the cells of the human body, oxygen molecules are used directly in a process of cellular respiration during which energy is released. In cellular respiration, glucose and oxygen yield carbon dioxide and water and energy is released in the form of adenosine triphosphate: C₆H₁₂O₆ (glucose) + O₂ (oxygen) → H₂O (water) + CO₂ (carbon dioxide) + ATP (adenosine triphosphate).</span>
All of the above are needed. Nucleotides are the basic building blocks of new DNA, ATP energy is needed because replication is an active process, and enzymes catalyze the reactions needed to carry it out (e.g. helicase to separate the strands to be replicated, DNA polymerase to build the new strands, and ligase to "glue" the fragments together).
Two important factors is temperature and liquid water.
