In oxidative photophosphorylation, the last 3 steps are as follows
`Q rarr C + "aa"_(3) rarr O_2`

Options

A. `Q rarr C` is `H^(+)` absorbing site
B. `"aa"_(3) rarr O_(2+)H^(+)` Yielding site
C. `Q rarr C` is `H^(+)` yielding site and `"aa"_(3) rarr O_2` is `H^(+)` absorbing site
D. No `H^(+)` is absorbed or released

Explanation

To solve the question regarding the last three steps in oxidative photophosphorylation, we need to break down the process step by step:

### Step-by-Step Solution:

1. **Understanding the Components**:
- In oxidative photophosphorylation, we have key components involved: Q (Coenzyme Q or Ubiquinone), C (Cytochrome C), and O2 (Oxygen).
- Q is an electron carrier that accepts electrons from NADH and FADH2 during the electron transport chain.

2. **Step 1 - Q to C**:
- The first step involves Q transferring electrons to C (Cytochrome C).
- During this transfer, Q releases hydrogen ions (H+) into the intermembrane space, contributing to the proton gradient.

3. **Step 2 - C to O2**:
- The second step involves Cytochrome C transferring electrons to Cytochrome a3.
- This step is crucial as it leads to the reduction of oxygen (O2).
- Oxygen acts as the final electron acceptor in the electron transport chain.

4. **Step 3 - Formation of Water**:
- When oxygen accepts the electrons, it combines with protons (H+) to form water (H2O).
- This process is essential as it helps maintain the flow of electrons through the chain and prevents a backlog of electrons.

5. **Conclusion**:
- The correct sequence of events in oxidative photophosphorylation is:
- Q → C (where Q yields hydrogen ions)
- C → O2 (where oxygen absorbs electrons and protons to form water).

### Final Answer:
The last three steps in oxidative photophosphorylation can be summarized as:
- Q → C (yielding H+)
- C → O2 (absorbing electrons to form H2O)