Release of oxygen during photosynthesis takes place in which of the following steps?

Options

A. Photophosphorylation
B. Reduction of NADP
C. Carbon fixation
D. Photolysis of water

Explanation

To determine the step in photosynthesis where oxygen is released, we can analyze the different processes involved in photosynthesis:

1. **Understanding Photosynthesis**: Photosynthesis occurs in two main stages: the light-dependent reactions and the light-independent reactions (Calvin cycle). The light-dependent reactions occur in the thylakoid membranes of the chloroplasts and involve capturing light energy.

2. **Identifying Key Steps**:
- **Photo Phosphorylation**: This process involves the production of ATP through the light reactions but does not release oxygen.
- **Reduction of NADP+**: In this step, NADP+ is reduced to NADPH, which is crucial for the Calvin cycle, but again, no oxygen is released.
- **Carbon Fixation**: This is part of the Calvin cycle where carbon dioxide is fixed into organic molecules. There is no release of oxygen in this step.
- **Photolysis of Water**: This is the process where water molecules are split into oxygen, protons, and electrons using light energy. This is the step where oxygen is released as a byproduct.

3. **Conclusion**: The correct answer to the question is that oxygen is released during the **photolysis of water**.

### Final Answer:
The release of oxygen during photosynthesis takes place in the step known as **photolysis of water**.