Which one of the following shows heterothallim?

Options

A. Rhizopus
B. Bacteri
C. Cycas
D. Ricinus

Answer

### Step-by-Step Solution:

1. **Understanding Heterothallism**:
- Heterothallism is a reproductive strategy where two different mating types (sexes) are required for sexual reproduction. This means that male and female gametes come from different individuals.

2. **Analyzing the Options**:
- We have four options to consider:
- A) Rhizopus
- B) Bacteria
- C) Cycus
- D) Resinus

3. **Evaluating Each Option**:
- **Option A: Rhizopus**:
- Rhizopus is a genus of fungi, commonly known as black bread mold. It exhibits heterothallism, as it requires two different mating types to reproduce sexually.
- **Option B: Bacteria**:
- Bacteria typically reproduce asexually through binary fission and do not exhibit heterothallism.
- **Option C: Cycus**:
- Cycus (Cycads) are seed plants and do not exhibit heterothallism in the same way fungi do.
- **Option D: Resinus**:
- Resinus is not commonly recognized in the context of heterothallism and does not display this reproductive strategy.

4. **Conclusion**:
- Based on the analysis, the only organism that shows heterothallism among the options is **Rhizopus**. Therefore, the correct answer is **A) Rhizopus**.