Which of the following is true about oxidation reactions?
a. oxidation reactions are the principal source of energy on earth.
b. all oxidation reactions are accompanied by reduction reactions.
c. the burning of wood in a fireplace and the metabolization of food by your body are oxidation reactions.
d. all of the above

The statement which is true about oxidation reactions is; Choice D; All of the above.

For choice A:

Oxidation reactions are characterized by the loss of electrons and the principal source of energy on Earth is by transfer of electrons. As such, Oxidation reactions are the principal source of energy on Earth.

For Choice B:

By convention, all oxidation reactions are accompanied by reduction reactions because the loss of electrons is accompanied by the gain of electrons.

For Choice C;

The burning of wood in a fireplace and the metabolization of food by your body are oxidation reactions. Combustion of wood is an oxidation reaction just like the metabolism of glucose is also an Oxidation reaction.

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D)can be increased in a closed system