Heterothallism is a device to prevent

Options

A. outbreeding
B. crossing over
C. inbreeding
D. none of these

Answer

### Step-by-Step Solution:

1. **Understanding Heterothallism**:
- Heterothallism refers to the production of two distinct types of thalli or hyphae in fungi, which are designated as plus (+) and minus (−) types.

2. **Function of Heterothallism**:
- The primary function of heterothallism is to facilitate sexual reproduction among fungi by ensuring that mating occurs between genetically dissimilar individuals, thereby promoting genetic diversity.

3. **Prevention of Inbreeding**:
- By requiring two different types of thalli (the plus and minus types) for reproduction, heterothallism prevents inbreeding, which is the mating of genetically similar or closely related organisms.

4. **Promotion of Outbreeding**:
- Heterothallism encourages outbreeding, which is the mating between genetically dissimilar organisms. This increases genetic variation and can lead to a healthier population.

5. **Conclusion**:
- Therefore, heterothallism is a device that prevents inbreeding among fungi.

### Final Answer:
Heterothallism is a device to prevent **inbreeding**.