The path of `CO_(2)` in the dark reaction of photosynthetic was successfully traced by the use of the following or The dark reaction is traced by

Options

A. `O_(2)^(18)`
B. `C^(14)`
C. `P^(32)`
D. X-rays

Answer

### Step-by-Step Solution:

1. **Understanding the Dark Reaction**: The dark reaction of photosynthesis, also known as the Calvin cycle, does not require light directly. It utilizes the products of the light-dependent reactions (ATP and NADPH) to convert carbon dioxide into glucose.

2. **Identifying the Key Experiment**: The question asks about tracing the path of carbon dioxide in the dark reaction. This tracing was accomplished through a specific experiment.

3. **Recognizing the Scientist**: The experiment was conducted by Melvin Calvin, who is known for his work on the Calvin cycle. He was awarded the Nobel Prize in Chemistry in 1961 for his discoveries related to photosynthesis.

4. **Use of Radioactive Carbon**: In his experiments, Calvin introduced carbon dioxide that contained a radioactive isotope, specifically carbon-14 (C-14). This allowed him to trace the incorporation of carbon dioxide into organic molecules during the dark reactions.

5. **Methodology**: Calvin used a single-celled green algae, Chlorella pyrenoidosa, in his experiments. He stopped the algae's growth at various stages and employed paper chromatography to analyze the radioactive compounds formed, which helped identify the chemical pathways involved in photosynthesis.

6. **Conclusion**: Based on the information provided, the correct answer to the question about which material was used to trace the dark reaction of photosynthesis is carbon-14 (C-14).

### Final Answer:
The path of CO₂ in the dark reaction of photosynthesis was successfully traced by the use of **C-14**.

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