When a plant photosynthesizes, the carbon used by the plant to construct organic molecules comes from .
a. COâ in the atmosphere
b. COâ in the soil
c. Organic carbon in the soil
d. Single carbon atoms in the atmosphere
e. Any of these sources

CO2 in the atmosphere

Explanation:

During photosynthesis, plants removes carbon dioxide in large amount from the atmosphere and then utilize the carbon atoms to build up organic molecules.

Thus, this removal of CO2 from the atmosphere provide a natural solution to prevent the gas accumulation in the atmosphere, which is often generated by human activities and natural causes.

both anaerobic and aerobic respiration use glucose (or other carbohydrates), proteins and lipids to produce atp and nadh. cell uses those energy molecules, obtained from food and   breaks them down during the chemical reactions of respiration. in anaerobic respiration, nadh is regenerated to nad+ by enzymes lactate dehydrogenase (lactate is produced, e.g. in muscle cells) or by alcohol dehydrogenase where ethanol is produced (alcohol fermentation), while in aerobic respiration, electrons from nadh are deposited in the mitochondria to regenerate nad+ (electron transport chain. anaerobic respiration produces 2 atp per molecule of glucose compared to aerobic respiration where about 38 atp molecules are produced.