Which of the following statements is true

Options

A. All chordates are vertebrates
B. All vertebrates are chordates
C. Invertebrates posses a tubular nerve cord
D. Non-chordates have a vertebral column

Answer

To determine which statement is true among the given options, we need to analyze each statement based on our understanding of vertebrates and caudates.

### Step-by-Step Solution:

1. **Understanding the Terms**:
- **Vertebrates**: These are animals that have a vertebral column (backbone) which replaces the notochord during their development.
- **Caudates (or Chordates)**: This group includes animals that possess a notochord at some stage of their life cycle. In caudates, the notochord is present throughout their life.

2. **Analyzing the Statements**:
- **Statement 1**: "All caudates are vertebrates."
- This statement is false. While all vertebrates are caudates, not all caudates are vertebrates. For example, some caudates like tunicates do not have a vertebral column.

- **Statement 2**: "All vertebrates are caudates."
- This statement is true. All vertebrates possess a notochord during their embryonic development, which is a characteristic of caudates.

- **Statement 3**: "Invertebrates possess a tubular nerve cord."
- This statement is misleading. Invertebrates do not possess a tubular nerve cord; this feature is characteristic of chordates, which include vertebrates and some invertebrates like cephalocordates.

- **Statement 4**: "Non-caudates have a vertebral column."
- This statement is false. Non-caudates, which include many invertebrates, do not have a vertebral column.

3. **Conclusion**:
- After analyzing all the statements, we find that the only true statement is **"All vertebrates are caudates."** Therefore, the correct answer is **Option B**.

### Final Answer:
**The correct statement is: All vertebrates are caudates (Option B).**

---