In the last stage of aerobic respiration, ...... is the final acceptor of electrons that originally resided in glucose.

Options

A. NADH
B. hydrogen
C. oxygen
D. water

Explanation

**Step-by-Step Solution:**

1. **Understanding Aerobic Respiration**: Aerobic respiration is a process that occurs in the presence of oxygen and involves the complete oxidation of glucose to produce energy.

2. **Glycolysis**: The first step in aerobic respiration is glycolysis. In this step, glucose (C6H12O6) is broken down into two molecules of pyruvate. This process also generates a small amount of ATP (energy) and NADH (an electron carrier).

3. **Krebs Cycle**: After glycolysis, the pyruvate enters the Krebs cycle (also known as the citric acid cycle). In this cycle, the pyruvate is further broken down, and more ATP, NADH, and FADH2 (another electron carrier) are produced.

4. **Electron Transport Chain (ETC)**: The final stage of aerobic respiration is the electron transport chain. Here, the NADH and FADH2 produced in the previous steps donate their electrons to a series of proteins embedded in the inner mitochondrial membrane.

5. **Final Electron Acceptor**: In the electron transport chain, the electrons are transferred through a series of cytochromes and ultimately accepted by oxygen. Thus, oxygen acts as the final electron acceptor in aerobic respiration.

6. **Conclusion**: Therefore, the answer to the question is that oxygen is the final acceptor of electrons that originally resided in glucose.

**Final Answer**: Oxygen

---