What must be done to coal before it can be used as fuel? It must be made to stick together.
It must be compressed into a very dense substance.
It must be ground into powder.
It must have flammable material added to it.

It must be ground into powder.

Explanation:

"Coal" is one of the nonrenewable resources that humans use for fuel. In order to produce energy, it needs to be burned first. However, efficient combustion happens when the coal is pulverized into fine powder first. This allows the coal to mixed with hot air sufficiently in order to release heat. This then allows the "generation of electricity" that is often used for cooking, lighting, cooling, transportation, healthcare, etc.

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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.