The substance that is a product of a fermentation reaction is ethanol or acetic acid. The correct option is C.
What is ethanol?
Ethanol, also called acetic acid, is an acid produced in the process of fermentation. It forms vinegar, 5 to 6% ethanol in water is vinegar. It is widely used in chemical labs, in homes for cooking, cleaning, etc.
Thus, the correct option is c, ethanol.
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