Which is dioecious?

Options

A. Taenia
B. Fasciola
C. Ascaris
D. None of the above

Answer

To determine which organism is dioecious among the given options, we need to understand the definitions of dioecious and monoecious.

### Step-by-Step Solution:

1. **Understand Dioecious**:
- Dioecious organisms have distinct male and female individuals. This means that male and female gametes are produced by separate individuals.

2. **Understand Monoecious**:
- Monoecious organisms have both male and female reproductive structures in the same individual. This means that one individual can produce both male and female gametes.

3. **Analyze the Options**:
- **Option A: Taenia**:
- Taenia (tapeworm) is monoecious because it has both male and female reproductive organs in the same individual.
- **Option B: Fasciola**:
- Fasciola (liver fluke) is also monoecious, meaning it has both male and female reproductive structures in the same individual.
- **Option C: Ascaris**:
- Ascaris (roundworm) is dioecious, as it has separate male and female individuals.
- **Option D: None of the above**:
- This option implies that none of the listed organisms are dioecious, which is incorrect since Ascaris is dioecious.

4. **Conclusion**:
- Based on the analysis, the correct answer is **Option C: Ascaris**, as it is the only organism among the options that is dioecious.

### Final Answer:
**C. Ascaris**