Isotopes popularly know to have been used in the study of photosynthesis are
or
Which of the following isotope of carbon was by Calvin to trace the path of carbon in photosynthesis

Options

A. `.^(11)C` and `.^(32)P`
B. `.^(15)C` and `.^(32)P`
C. `.^(16)C` and `.^(15)N`
D. `.^(14)C` and `.^(18)O`.

Answer

To solve the question regarding the isotopes used in the study of photosynthesis, particularly the one used by Calvin to trace the path of carbon, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Context**: The question is about the isotopes used in photosynthesis studies, specifically by Melvin Calvin, who is known for the Calvin cycle.

2. **Identify the Isotopes**: Calvin used isotopes to trace the path of carbon during photosynthesis. The two isotopes commonly associated with his experiments are:
- Carbon-14 (C-14)
- Oxygen-18 (O-18)

3. **Determine the Main Isotope Used for Carbon Tracing**: Among these, the isotope specifically used by Calvin to trace the path of carbon in photosynthesis is Carbon-14 (C-14).

4. **Conclusion**: Therefore, the correct answer to the question is that the isotope of carbon used by Calvin to trace the path of carbon in photosynthesis is Carbon-14.

### Final Answer:
The isotope of carbon used by Calvin to trace the path of carbon in photosynthesis is **Carbon-14**.

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