Oxygen is not produced during photosynthesis by

Options

A. Chara
B. Cycas
C. Nostoc
D. Green sulphur bacteria

Answer

To answer the question "Oxygen is not produced during photosynthesis by," we need to analyze the options provided: Cara, Cycus, Nostoc, and Green Sulphur Bacteria.

### Step-by-Step Solution:

1. **Understanding Photosynthesis**:
- Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy, producing oxygen as a byproduct. This typically involves the use of water (H2O) and carbon dioxide (CO2).

2. **Identifying the Organisms**:
- **Cara**: This refers to a genus of green algae, which performs photosynthesis and produces oxygen.
- **Cycus**: This is a genus of cycads, which are seed plants that also perform photosynthesis and produce oxygen.
- **Nostoc**: This is a genus of cyanobacteria (blue-green algae) that can perform photosynthesis and produce oxygen.
- **Green Sulphur Bacteria**: These are a group of bacteria that do not produce oxygen during photosynthesis. Instead of using water, they utilize hydrogen sulfide (H2S) for their photosynthetic process.

3. **Analyzing the Options**:
- Since Cara, Cycus, and Nostoc are all capable of producing oxygen through the typical photosynthetic process, they do not fit the criteria of the question.
- Green Sulphur Bacteria, on the other hand, do not produce oxygen because they use H2S instead of water.

4. **Conclusion**:
- Therefore, the correct answer is **Green Sulphur Bacteria** as they do not produce oxygen during photosynthesis.

### Final Answer:
Oxygen is not produced during photosynthesis by **Green Sulphur Bacteria**.

---