Answer:
i think its the first one (I'm not sure tho but i will leave the explianation)
Explanation:
Organic molecules are usually composed of carbon atoms in rings or long chains, to which are attached to other atoms of such elements as hydrogen, oxygen, and nitrogen.
(hope its clear )
Because it can respire anaerobically, without oxygen.
Hope this helps!
The rungs are composed of hydrogen bonded paired Nitrogenous Bases. These pairings are Adenine to Thymine and Guanine to Cytosine.
Anatomical or molecular homologous structures
