Bt cotton is resistant to:

Options

A. insects
B. herbicides
C. salt
D. drought

Answer

**Step-by-Step Solution:**

1. **Understanding Bt Cotton**:
- Bt cotton is a genetically modified organism (GMO) that has been engineered to be resistant to certain pests.

2. **Identifying the Source of Resistance**:
- The resistance in Bt cotton comes from a gene known as the cry gene, which is derived from the bacterium *Bacillus thuringiensis*.

3. **Mechanism of Action**:
- The cry gene enables the cotton plant to produce a protein called Bt toxin (endotoxin), which is toxic to specific herbivorous insects.

4. **Conclusion**:
- As a result of this genetic modification, Bt cotton is primarily resistant to insects, particularly those that feed on cotton plants.

5. **Final Answer**:
- Therefore, the correct answer to the question "Bt cotton is resistant to:" is **insects**.

---