What condition is required for fermentation to occur? a. when the energy production cycle ends of the krebs cycle b. when oxygen levels within a cell are too low for aerobic respiration c. when 20 molecules of atp are needed d. when a glucose molecule needs to break down completely

The answer is B.

Fermentation(an anaerobic process) is a way of harvesting chemical energy without using either oxygen or any electron transport chain.

Fermentation consists of glycolysis plus reaction that regenerate NAD+ by transferring electrons from NADH to pyruvate or derivatives of pyruvate.

There are many types of fermentation, lactic acid fermentation and alcohol fermentation are the most common two.

The correct answer would be b