Pseudocoelom is present in a

Options

A. earthworm
B. tapeworm
C. roundworm
D. mammal

Answer

**Step-by-Step Solution:**

1. **Understanding Pseudocoelom**:
- Pseudocoelom is a type of body cavity that is not completely lined by mesoderm. It is found in certain organisms and serves as a space for the internal organs.

2. **Analyzing the Options**:
- **Option A: Earthworm**: Earthworms possess a true coelom, which is a body cavity fully lined by mesoderm. Therefore, pseudocoelom is absent in earthworms.
- **Option B: Tapeworm**: Tapeworms are flatworms and have a solid body without a body cavity, so they do not possess a pseudocoelom.
- **Option C: Roundworm**: Roundworms (such as nematodes) have a pseudocoelom. Their body cavity is not entirely lined by mesoderm, which qualifies it as a pseudocoelom.
- **Option D: Mammals**: Mammals have a true coelom, which is derived from the mesoderm, meaning they do not have a pseudocoelom.

3. **Conclusion**:
- Based on the analysis, the only organism from the given options that possesses a pseudocoelom is the roundworm. Therefore, the correct answer is **Option C: Roundworm**.