`C_(4)` pathway of `CO_(2)` fixation was discovered by

Options

A. Blackman
B. Hatch and Slack
C. Emerson and Arnold
D. Arnon.

Answer

To solve the question regarding who discovered the C4 pathway of CO2 fixation, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the C4 Pathway**: The C4 pathway is a method of carbon fixation in plants where carbon dioxide is initially fixed into a four-carbon compound, specifically oxaloacetic acid. This process is crucial for certain plants, known as C4 plants, which have adapted to efficiently fix carbon in environments with high temperatures and light intensity.

2. **Identify the Scientists Involved**: The question provides several names as options: Blackman, Hatchins, Lack, Emerson and Arnold, and Arnon. We need to identify which of these scientists were involved in the discovery of the C4 pathway.

3. **Research the Discovery**: The C4 pathway was discovered by two scientists, Hatch and Slack, in 1966. They described the process and its significance in certain plants, which is why it is also referred to as the Hatch-Slack pathway.

4. **Eliminate Incorrect Options**:
- Blackman is known for his work on the dark reactions of photosynthesis.
- Emerson and Arnold conducted experiments related to light and dark reactions but did not discover the C4 pathway.
- Lack is not associated with the discovery of the C4 pathway.
- Arnon is known for his work in photosynthesis but not specifically for the C4 pathway.

5. **Conclusion**: Based on the above information, the correct answer to the question is **Hatch and Slack**.

### Final Answer:
The C4 pathway of CO2 fixation was discovered by **Hatch and Slack**.

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