This is the answer for many reasons. First off, it is not one of the ending compounds. It is only the end compound for photosynthesis. Second, it does not react to water as that is yet again photosynthesis. It does not react with carbon dioxide as carbon dioxide is what initially creates oxygen within cellular respiration.
Carbon atoms have 4 valence electrons. That allows them to make 4 covalent bonds. That means they can make really big molecules. All the organic molecules have Carbon in them.
