Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because

Options

A. bacteria are resistant to the toxin.
B. toxin is immature.
C. toxin is inactive.
D. bacteria enclose toxin in a special sac.

Explanation

### Step-by-Step Solution:

1. **Understanding Bt Toxin**: Bt toxin is a protein produced by the bacterium *Bacillus thuringiensis*. It is known for its insecticidal properties.

2. **Inactive Form**: The Bt toxin is produced in an inactive form known as protoxin. This means that while the bacteria can produce the toxin, it does not pose a threat to the bacteria itself.

3. **Activation in Insects**: When the protoxin enters the gut of an insect, it encounters a specific pH environment that activates it. The gut conditions transform the protoxin into its active form, which is toxic to insects.

4. **Reason for Non-toxicity to Bacteria**: Since the Bt toxin remains in its inactive form within the bacteria, it does not harm the bacteria itself. The activation of the toxin only occurs in the specific environment of an insect's gut.

5. **Conclusion**: Therefore, the reason that crystals of Bt toxin do not kill the bacteria that produce them is that they are synthesized in an inactive form, which is only converted to an active, toxic form under specific conditions found in the gut of certain insects.