Vertebral column is a modified

Options

A. Nerve cord
B. Notochord
C. Umbilical chord
D. Urochordata

Answer

To solve the question "Vertebral column is a modified," we will analyze the options provided and understand the concepts related to the vertebral column and its origin.

### Step-by-Step Solution:

1. **Understanding the Vertebral Column**: The vertebral column, also known as the backbone, is a crucial structure in vertebrates. It provides support and protects the spinal cord.

2. **Identifying the Options**: The options given are:
- A. Nerve cord
- B. Notochord
- C. Umbilical cord
- D. Urocordata

3. **Analyzing Each Option**:
- **A. Nerve cord**: This is part of the nervous system and does not directly relate to the structure of the vertebral column.
- **B. Notochord**: This is a flexible rod-like structure found in the embryos of all chordates. In vertebrates, the notochord is replaced by the vertebral column during development.
- **C. Umbilical cord**: This structure connects a developing fetus to the placenta and is not related to the vertebral column.
- **D. Urocordata**: This is a subphylum of chordates that includes tunicates, which do not have a vertebral column.

4. **Conclusion**: The vertebral column is derived from the notochord during the development of vertebrates. Therefore, the correct answer is **B. Notochord**.

### Final Answer:
The vertebral column is a modified **B. Notochord**.