The trigger for activation of toxin of Bacillus thuringiensis is

Options

A. acidic pH of stomach
B. high temperature
C. alkaline pH of gut
D. mechanical action in the insect gut

Answer

To determine the trigger for the activation of the toxin of Bacillus thuringiensis (Bt), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Bacillus thuringiensis (Bt)**:
- Bacillus thuringiensis is a bacterium that produces a toxin which is harmful to certain insects. This toxin is initially in an inactive form known as protoxin.

**Hint**: Remember that the toxin is not active until it undergoes a transformation.

2. **Ingestion by Insects**:
- When an insect consumes the Bt toxin, it ingests the inactive protoxin.

**Hint**: Think about what happens to substances when they enter the digestive system of an insect.

3. **Activation of the Toxin**:
- The inactive protoxin is converted into its active form when it reaches the insect's gut. This conversion is crucial for the toxin to exert its effects.

**Hint**: Consider the conditions within the insect's digestive system that could lead to this conversion.

4. **Role of pH**:
- The activation of the Bt toxin occurs specifically due to the alkaline pH found in the gut of the insect. The alkaline environment facilitates the transformation of the protoxin into the active toxin.

**Hint**: Recall the difference between acidic and alkaline pH levels and how they can affect biochemical reactions.

5. **Elimination of Other Options**:
- The other options provided (acidic pH of stomach, high temperature, mechanical action in the insect gut) do not trigger the activation of the toxin. The acidic pH of the stomach does not activate the toxin, and high temperature and mechanical action do not play a role in this specific activation process.

**Hint**: Focus on the specific conditions that are necessary for the activation of the toxin rather than general digestive processes.

### Conclusion:
The correct answer to the question is that the trigger for the activation of the toxin of Bacillus thuringiensis is the **alkaline pH of the gut**.