Urochordata or tunicata is

Options

A. Phylum
B. Sub-group
C. Sub-phylum
D. Class

Explanation

**Step-by-Step Solution:**

1. **Identify the Classification**: The term "Urochordata" or "Tunicata" refers to a specific group within the animal kingdom. We need to determine what category it falls under in biological classification.

2. **Examine the Options**: The options provided are:
- Phylum
- Subgroup
- Subphylum
- Class

3. **Understanding Urochordata/Tunicata**: Urochordata, also known as Tunicata, is recognized as a subphylum within the phylum Chordata. This classification is crucial for understanding the hierarchical structure of biological taxonomy.

4. **Characteristics of Urochordata**: Members of this subphylum are primarily marine organisms. They are mostly sedentary (fixed in one place) but can also be free-swimming. They can be solitary or colonial, with sizes ranging from 0.25 mm to 250 mm.

5. **Body Structure**: Adult Urochordates have a body covered by a protective layer called a "tunic," which is secreted by mesodermal cells. They lack segmentation and paired appendages, and while adults do not have a tail, it is present in their larval stage.

6. **Conclusion**: Based on the classification and characteristics, Urochordata or Tunicata is correctly classified as a subphylum.

7. **Final Answer**: Therefore, the correct answer is **Subphylum**.

---