Action of insulin was first demonstrated by

Options

A. Banting and Best
B. Darwin
C. Lamarck
D. Watson and Crick.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks who first demonstrated the action of insulin. This involves identifying the historical figure or group that was pivotal in the discovery and understanding of insulin's role in regulating blood sugar levels.

2. **Reviewing the Options**: The options provided are:
- A) Bantingen-Best
- B) Darwin
- C) Lamarck
- D) Watson and Crick

3. **Analyzing Each Option**:
- **Darwin**: Known for his theory of natural selection, not related to insulin.
- **Lamarck**: Proposed the theory of inheritance of acquired characteristics, also not related to insulin.
- **Watson and Crick**: Famous for discovering the double helical structure of DNA, again not related to insulin.
- **Bantingen-Best**: They are known for their work on insulin, specifically for its discovery and purification.

4. **Identifying the Correct Answer**: Based on the analysis, Bantingen-Best is the correct answer as they were the first to demonstrate the action of insulin and made it available for diabetes treatment.

5. **Conclusion**: Therefore, the action of insulin was first demonstrated by Bantingen-Best.

**Final Answer**: Bantingen-Best

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