Identify a triploblastic animal lacking true coelom.

Options

A. Ascaris
B. Cockroach
C. Pheretima
D. Rana

Answer

To solve the question of identifying a triploblastic animal that lacks a true coelom, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Terms**:
- **Triploblastic**: This refers to animals that develop from three embryonic germ layers: ectoderm, mesoderm, and endoderm.
- **True Coelom**: A body cavity that is completely lined by mesoderm. Animals with a true coelom are called coelomates.

2. **Identify Animal Groups**:
- Animals can be classified based on the presence or absence of a coelom:
- **Acoelomates**: Animals without a coelom (e.g., Platyhelminthes).
- **Pseudocoelomates**: Animals with a pseudocoelom, which is not completely lined by mesoderm (e.g., Aschelminthes).
- **Coelomates**: Animals with a true coelom (e.g., Annelida, Arthropoda).

3. **Focus on Triploblastic Animals**:
- Since we are looking for triploblastic animals, we can exclude diploblastic animals (which only have ectoderm and endoderm).

4. **Narrow Down the Options**:
- Since the question specifies that we need a triploblastic animal that lacks a true coelom, we can focus on:
- **Platyhelminthes** (e.g., flatworms) which are acoelomates and lack a true coelom.
- **Aschelminthes** (e.g., roundworms) which are pseudocoelomates and have a pseudocoelom.

5. **Identify the Correct Answer**:
- Among the options, **Ascaris** (a roundworm) is a pseudocoelomate, while **Platyhelminthes** (like flatworms) are acoelomates.
- Since the question asks for an animal that lacks a true coelom, **Ascaris** is not the correct answer because it has a pseudocoelom.
- The correct answer is a representative from **Platyhelminthes**, which is an acoelomate.

6. **Conclusion**:
- The triploblastic animal that lacks a true coelom is **Platyhelminthes** (e.g., flatworms).

### Final Answer:
Platyhelminthes (e.g., flatworms) is the triploblastic animal lacking a true coelom.