why does the oxygen atom in a water molecule have a negative charge?
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a. water is made of two ionic bonds.
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b. oxygen attracts electrons more strongly than hydrogen does.
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c. water is a nonpolar molecule.
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d. hydrogen bonding pulls electrons toward oxygen.

The answer is B.

Explanation:

A is incorrect because water is a molecule with covalent bonds.

C is incorrect because water is very much polar, since Oxygen has a relatively higher electronegativity than Hydrogen (so the difference of their electronegativities would be greater than 0.3 and less than 1.7).

D is incorrect because the bonds between elements in the water molecules is  not hydrogen bonding since water is a molecule in its own right, with strong bonds.

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.