Final answer:
In the absence of oxygen, the waste product of glycolysis is either lactate during lactic acid fermentation or ethanol and carbon dioxide during alcoholic fermentation.
Step-by-step explanation:
The waste product of glycolysis in the absence of oxygen is typically lactic acid during lactic acid fermentation, or ethanol and carbon dioxide during alcoholic fermentation. Fermentation allows cells to regenerate NAD+ which is essential for glycolysis to continue in the absence of oxygen. Therefore, the options given, the correct end product of glycolysis under anaerobic conditions (in absence of oxygen) would be lactate, as it is the molecule that is used to regenerate NAD+ from the reduction of pyruvate.