Which one of the following kinds of animals are triploblastic

Options

A. Flatworms
B. Sponges
C. Ctenophores
D. Corals

Explanation

To determine which kind of animals are triploblastic, we need to understand the concept of germ layers in embryonic development. Here’s a step-by-step solution:

### Step-by-Step Solution:

1. **Understand Germ Layers**:
- Animals can be classified based on the number of embryonic germ layers they develop from. The three types are:
- **Diploblastic**: Animals with two germ layers (ectoderm and endoderm).
- **Triploblastic**: Animals with three germ layers (ectoderm, mesoderm, and endoderm).

2. **Identify Triploblastic Animals**:
- Triploblastic animals possess a mesoderm layer in addition to the ectoderm and endoderm. This allows for more complex body structures and systems.

3. **Examples of Triploblastic Animals**:
- Flatworms (Phylum Platyhelminthes) are one of the earliest groups of triploblastic animals. They have all three germ layers.
- Other examples of triploblastic animals include annelids (segmented worms), mollusks, arthropods, and vertebrates.

4. **Differentiating from Diploblastic Animals**:
- Diploblastic animals, such as sponges (Phylum Porifera), ctenophores (sea walnuts), and corals (Phylum Cnidaria), only have two germ layers (ectoderm and endoderm) and lack a mesoderm.

5. **Conclusion**:
- Based on the classification, the correct answer to the question "Which one of the following kinds of animals are triploblastic?" is **flatworms**, which belong to the phylum Platyhelminthes.