Final answer:
The correct answer is pyruvic acid and oxygen, which enter the mitochondria to complete the process of cellular respiration. Pyruvic acid enters the Krebs cycle and oxygen is used in the electron transport chain to produce ATP. So the correct option is b.
Step-by-step explanation:
The substances that must enter the mitochondria for cellular respiration to be completed are pyruvic acid and oxygen. This makes option b the correct answer. Pyruvic acid is produced in the cytoplasm of the cell during glycolysis, which is the first step of cellular respiration. It then enters the mitochondria where it is converted into acetyl CoA. This acetyl CoA enters the Krebs cycle (or citric acid cycle), releasing carbon dioxide and transferring electrons to NADH and FADH2. Oxygen is essential as the final electron acceptor in the electron transport chain and is necessary to produce a large amount of ATP, which is the main energy currency of the cell.
Oxygen and pyruvic acid are used up during cellular respiration and the main products produced are ATP and water, as well as carbon dioxide as a waste product. In summary, the two products of aerobic cellular respiration listed in option 8 are ATP and H₂O (option d).