Which one of the following groups of animals is bilaterally symmetrical and triploblastic
(a) Sponges
(b) Coelenterates (Cnidarians)
(c) Aschelminthes (round worms)
(d) Ctenophores

Options

A. Sponges
B. Coelenterates ( Cnidarians )
C. Aschelminthes ( round worms )
D. Ctenophores

Answer

To determine which group of animals is bilaterally symmetrical and triploblastic, we need to analyze each option based on their characteristics.

### Step-by-Step Solution:

1. **Understanding Key Terms**:
- **Bilateral Symmetry**: This means the organism can be divided into two identical halves along one plane.
- **Triploblastic**: This refers to organisms that have three germ layers: ectoderm, mesoderm, and endoderm.

2. **Analyzing Each Option**:
- **(a) Sponges**:
- Sponges are asymmetrical and do not have true tissues. They are classified as diploblastic, meaning they have two germ layers (ectoderm and endoderm).
- **(b) Coelenterates (Cnidarians)**:
- Coelenterates exhibit radial symmetry and are also diploblastic. They have two germ layers.
- **(c) Aschelminthes (Round Worms)**:
- Aschelminthes are bilaterally symmetrical and are triploblastic, possessing three germ layers.
- **(d) Ctenophores**:
- Ctenophores can exhibit biradial symmetry and are generally classified as diploblastic, meaning they have two germ layers.

3. **Conclusion**:
- Based on the analysis, the only group that is both bilaterally symmetrical and triploblastic is **Aschelminthes (Round Worms)**.
- Therefore, the correct answer is **(c) Aschelminthes**.

### Final Answer:
(c) Aschelminthes (round worms)

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