Aurelia has

Options

A. Two smooth oral arms
B. Two nematoblast rich oral arms
C. Four tentacles
D. Four cnidoblast rich oral arms.

Answer

**Step-by-Step Solution:**

1. **Identify the Organism**: The question asks about Aurelia, which is a type of jellyfish. It belongs to the phylum Cnidaria.

2. **Understand Cnidaria Characteristics**: Cnidarians are characterized by the presence of specialized cells called cnidoblasts, which contain organelles known as cnidocysts. These structures are used for capturing prey.

3. **Describe the Structure of Aurelia**: Aurelia has a distinct umbrella-shaped body known as the medusa. This is a key feature of jellyfish.

4. **Identify Key Features**: In Aurelia, the mouth is located on the underside of the medusa and is surrounded by four oral arms. These arms are important for feeding.

5. **Examine the Gonads**: Aurelia is a unisexual organism, meaning it has either male or female reproductive organs. It possesses four gonads, which can be either testes or ovaries.

6. **Evaluate the Options**:
- **Option 1**: Two smooth oral arms - Incorrect, as Aurelia has four oral arms.
- **Option 2**: Two nematoblast-rich oral arms - Incorrect, as there are four oral arms.
- **Option 3**: Four tentacles - Incorrect, as Aurelia has numerous tentacles, not just four.
- **Option 4**: Four nidoblast-rich oral arms - Correct, as the oral arms contain nidoblasts.

7. **Conclusion**: The correct answer is that Aurelia has four nidoblast-rich oral arms.