Water, a stable liquid, is formed when two flammable gases, hydrogen and oxygen, combine. What has happened? O An atom has been created.
O A compound has been created,
O A mixture has been created,
An element has been created

A compound has been created

Explanation:

Remember you cannot create an atom nor can you create an element so An atom has been created and An element has been created is incorrect. Also, a compound is something that is chemically bound and cannot be separated unless applied a chemical change, which is applicable to water. It cannot be a mixture since mixtures can be separated physically, which you can't do with water.

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.

maybe because its impossible for balloons to lift a whole entire house.