Choose the correct definition of biocontrol.

Options

A. Used for developing immunity in the cattle
B. Use of microbes to control plant diseases
C. Use of microbe to control cattle diseases
D. Alteration of defective gene

Answer

### Step-by-Step Solution:

1. **Understanding Biocontrol**:
- Biocontrol refers to the use of living organisms, such as microbes, to control pests and diseases in plants. This method is environmentally friendly and sustainable compared to chemical pesticides.

2. **Analyzing the Options**:
- **Option 1**: "Used for developing immunity in the cattle."
- This option is incorrect as biocontrol specifically relates to plants, not cattle.
- **Option 2**: "Use of microbes to control plant disease."
- This option accurately describes biocontrol, as it involves using microbes to protect plants from diseases caused by other microbes, insects, or pests.
- **Option 3**: "Use of microbes to control cattle disease."
- This option is incorrect because it pertains to animal health rather than plant health.
- **Option 4**: "Alteration of defective Zeno."
- This option is also incorrect and does not relate to the definition of biocontrol.

3. **Conclusion**:
- After analyzing all the options, the correct definition of biocontrol is found in **Option 2**: "Use of microbes to control plant disease."

### Final Answer:
- The correct definition of biocontrol is **Option 2: Use of microbes to control plant disease.**