You have just started brewing beer at home, and your first batch is now ready. You used the yeast Saccharomyces cerevisia, which can perform both aerobic cellular respiration and fermentation. When you test the beer, you determine that the alcohol content is almost zero. What could have been present in the fermentation reaction apparatus that caused this problem?
a. oxygenb. carbon dioxidec. pyruvic acidd. glucose

Fermentation is the biological process behind the creation of beer. Saccharomyces cerevisia, the yeast used for beer's production can perform both aerobic cellular respiration and fermentation. In the presence of oxygen, Saccharomyces cerevisia would undergo aerobic cellular respiration and will broke glucose to carbon dioxide and will produce energy. In the absence of oxygen, the yeast would undergo fermentation and the glucose will be converted into ethanol (alcohol). If after the brewing procedure the alcohol content is almost zero, it is possible that oxygen is present in the fermentation reaction apparatus. Under the presence of oxygen Saccharomyces cerevisia will undergo aerobic cellular respiration not fermentation.