The Bt toxin is not human beings because

Options

A. the pro Bt toxin activation requires temperature above human body temperature
B. the Bt toxin recognises only insect-specific targets
C. the pro Bt toxin activation requires pH lower than that present in human stomach
D. conversion of pro Bt toxin to Bt toxin takes place in highly alkaline conditions.

Explanation

**Step-by-Step Solution:**

1. **Understanding Bt Toxin**: Bt toxin is a protein produced by the bacterium Bacillus thuringiensis. It is primarily used as an insecticide to target specific pests.

2. **Activation of Bt Toxin**: The Bt toxin exists in an inactive form known as protoxin. This protoxin does not harm the bacterium itself or other organisms until it is activated.

3. **Conditions for Activation**: The activation of the Bt toxin occurs when it is ingested by insects. This activation is facilitated by the alkaline pH found in the gut of these insects.

4. **Human Digestive Environment**: In contrast, the human stomach has a highly acidic environment due to the presence of gastric juices, which contain hydrochloric acid (HCl). This acidic condition is not conducive to the activation of the Bt toxin.

5. **Conclusion**: Since the activation of Bt toxin requires alkaline conditions, and humans have an acidic stomach environment, the Bt toxin does not get activated in humans and therefore is not harmful to them.

6. **Final Answer**: The Bt toxin is not harmful to human beings because the conversion of the inactive protoxin to the active Bt toxin occurs only in alkaline conditions, which are not present in the human digestive system.

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