`2H_(2)A+CO_(2)overset("light")to2A+CH_(2)O+H_(2)O`
in this given equation H2A represents to H2S, now it would be applicable on :-

Options

A. All prokaryotes
B. All eukaryotes
C. Only some prokaryotes
D. Only some eukaryotes

Answer

To solve the question regarding the equation `2H_(2)A + CO_(2) overset("light") to 2A + CH_(2)O + H_(2)O`, where H2A represents hydrogen sulfide (H2S), we need to analyze the context of the equation and the organisms involved.

### Step-by-Step Solution:

1. **Identify H2A**: In the equation, H2A is specified to be hydrogen sulfide (H2S). This compound serves as a hydrogen donor in the photosynthetic process.

2. **Understand the Organisms**: The question is asking which type of organisms this equation applies to. The options provided are:
- Eukaryotes
- Prokaryotes
- Some Prokaryotes
- Some Eukaryotes

3. **Recall the Characteristics of Prokaryotes and Eukaryotes**:
- Prokaryotes are unicellular organisms that lack a nucleus and membrane-bound organelles. They include bacteria.
- Eukaryotes are organisms whose cells have a nucleus and membrane-bound organelles, including plants and animals.

4. **Research Background**: The equation is derived from the research of Neil Wayne, who studied purple and green sulfur bacteria. These bacteria are known to utilize hydrogen sulfide as a hydrogen donor during photosynthesis.

5. **Determine the Correct Option**: Since H2S is a hydrogen donor in the context of photosynthesis for certain bacteria, and these bacteria are classified as prokaryotes, the equation is applicable to prokaryotes.

6. **Conclusion**: The correct answer is that the equation is applicable to all prokaryotes.

### Final Answer:
The equation is applicable to **all prokaryotes**.

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