Diploblastic, multicellular animals with coelenteron.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about animals that are diploblastic, multicellular, and have a coelenteron.

2. **Defining Key Terms**:
- **Diploblastic**: This term refers to organisms that have two primary germ layers: the outer layer (epidermis) and the inner layer (gastrodermis).
- **Multicellular**: This indicates that the organism is made up of multiple cells.
- **Coelenteron**: This is the central digestive cavity in certain animals, also known as the gastrovascular cavity.
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