Flat worms are

Options

A. Dipoblastic
B. Triploblastic
C. Monoblastic
D. None of the above

Answer

**Step-by-Step Solution:**

1. **Identify the Phylum**: Flatworms belong to the phylum Platyhelminthes. This is the first step in understanding what flatworms are.

2. **Characteristics of Flatworms**: Flatworms are characterized by their dorso-ventral flattening, which gives them a bilateral symmetry. This means their body can be divided into two equal halves along one plane.

3. **Habitat**: Most flatworms are endoparasites, meaning they live inside the bodies of other organisms. This is an important aspect of their biology.

4. **Examples of Flatworms**: Notable examples of flatworms include tapeworms and liver flukes. These examples help illustrate the diversity within the phylum.

5. **Germ Layers**: Flatworms are triploblastic organisms. This means they have three embryonic germ layers: ectoderm, mesoderm, and endoderm. This is a key distinction from diploblastic organisms, which only have two germ layers.

6. **Diploblastic vs. Triploblastic**: Diploblastic organisms, such as those in the phyla Porifera, Cnidaria, and Ctenophora, have only two germ layers (ectoderm and endoderm) with a layer called mesoglia in between. In contrast, flatworms have a mesoderm layer, making them triploblastic.

7. **Conclusion**: Based on the characteristics and classification, we conclude that flatworms are triploblastic organisms.

**Final Answer**: Flatworms are triploblastic organisms belonging to the phylum Platyhelminthes, characterized by their dorso-ventral flattening and typically being endoparasitic.

---