The answer is; C
Mitochondria are significant in the aerobic respiration of glucose in the body. The Krebs cycle occurs in the matrix of the mitochondria when there is available oxygen for aerobic respiration. This is usually preceded by glycolysis that breaks down glucose anaerobically in the cytosol to produce pyruvate. Pyruvate enters the Krebs cycle if there is available oxygen. However, if there are no oxygen, or mitochondria, in this case, the pyruvate is converted to lactate.