Final answer:
Carbon dioxide (CO₂) is released during the oxidation of pyruvate and the Krebs cycle. The correct answer to the student's question is option C. Additionally, FADH₂ is the only compound among the choices given that is produced solely in the Krebs cycle.
Step-by-step explanation:
During the complete catabolism of glucose, carbon dioxide (CO₂) is released during the Krebs cycle and the oxidation of pyruvate. Pyruvate, after glycolysis, is converted into acetyl CoA in a process that releases CO₂, and this acetyl CoA then enters the Krebs cycle.
Furthermore, during the Krebs cycle additional molecules of CO₂ are released. To address the provided question, the correct answer is C. Krebs cycle and oxidation of pyruvate.
On the other hand, the compound that is produced only in the Krebs cycle from the options given is FADH₂. This means that the correct answer to the question about the complete catabolism of glucose is D. FADH₂.