What chemical compound is crucial to marine life and how it is disappearing

The answer is nitrogen. It is usually regarded as a growth-limiting factor for primary producers such as phytoplankton. It is usually taken up in the ‘fixed’ form of ammonium. It is converted from dissolved nitrogen gas in ocean surface to a ‘fixed’ form by particular microbes. Due to increasing global temperatures, as a result of global warming, the ocean temperatures have increased hence oceans hold less dissolved oxygen than they used to. The low oxygen concentration in the oceans induces the loss of nitrogen from oceans through increased activity of micro-organisms that are significant in denitrification. This rate becomes higher than that of nitrification that fixes nitrogen in the oceans.   

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.

it's not c. i took the quiz and got it wrong. so my best guess is b.

have a great day, and hope this .