Bacillus thuringiensis (Bt) strains have been used for designing novel

Options

A. Biofertilizers
B. Bio-metallurgical techniques
C. Bio-mineralization processes
D. Bioinsecticidal plants

Answer

### Step-by-Step Solution:

1. **Understanding Bacillus thuringiensis (Bt)**:
- Bacillus thuringiensis is a bacterium that produces proteins toxic to certain insects. It is commonly found in soil and is known for its insecticidal properties.

2. **Identifying the Applications of Bt**:
- Bt strains are primarily used in agriculture for pest control. They are incorporated into plants to create bio-insecticidal properties.

3. **Evaluating the Options**:
- **Biofertilizers**: These are living organisms used to enhance soil fertility, typically not directly related to Bt.
- **Biometallurgical Techniques**: These involve the extraction of metals using biological processes, which is not the primary application of Bt.
- **Biomineralization Process**: This refers to the process of minerals being formed by biological activity, which does not directly involve Bt.
- **Bio-Insecticidal Plants**: This option directly relates to the use of Bt strains to develop plants that can produce insecticidal proteins, making them resistant to pests.

4. **Conclusion**:
- The most appropriate application of Bacillus thuringiensis strains is in the design of **bio-insecticidal plants**. These plants can produce toxins that specifically target harmful insects, thereby providing an environmentally friendly pest control method.

### Final Answer:
Bacillus thuringiensis (Bt) strains have been used for designing **bio-insecticidal plants**.

---