Question

Under what conditions does a cell use fermentation instead of cellular respiration?

Answer 1

Absence of oxygen

fermentation is an anaerobic (meaning doesn't require oxygen) process 

Answer 2

Absence of oxygen

A cell use fermentation instead of cellular respiration in the absence of oxygen.

Fermentation is an anaerobic (without oxygen) cellular process in which an organism degrades, and converts an organic food (such as sugar) into simpler compounds such as an alcohol or acid with the production of chemical energy (adenosine triphosphate). This process takes place in muscle cells of animals, in yeast cells, and in bacteria.