Platyhelminthes are characterised by

Options

A. radial symmetry
B. diploblastic nature
C. acoelomate nature
D. segmentation

Answer

### Step-by-Step Solution:

1. **Understanding the Characteristics of Platyhelminthes**:
- Platyhelminthes, commonly known as flatworms, have specific characteristics that define their classification.

2. **Symmetry**:
- Platyhelminthes exhibit **bilateral symmetry**, meaning their body can be divided into two equal halves along one plane. This is different from radial symmetry, where the body can be divided into similar parts around a central axis.

3. **Germ Layer Composition**:
- They are **triploblastic**, which means they have three primary germ layers: ectoderm, mesoderm, and endoderm. This is in contrast to diploblastic organisms, which only have two germ layers.

4. **Body Cavity**:
- Platyhelminthes are classified as **acoelomates**, meaning they lack a true body cavity (coelom). This is an important characteristic that differentiates them from other groups that possess a body cavity.

5. **Segmentation**:
- They do not exhibit **segmentation**; their bodies are not divided into repeated segments, which is a characteristic seen in other animal phyla like annelids.

6. **Conclusion**:
- Based on these characteristics, the correct answer to the question "Platyhelminthes are characterised by" is that they are **acoelomate** (absence of body cavity) and **triploblastic** (three germ layers) with **bilateral symmetry** and **lack of segmentation**.

### Final Answer:
Platyhelminthes are characterized by being **triploblastic**, **acoelomate**, having **bilateral symmetry**, and the **absence of segmentation**.

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