Correct statement of the following is

Options

A. all vertebrates are chordates
B. all chordates are vertebrates
C. all invertebrates are chordates
D. all protochordates are vertebrates

Answer

To determine the correct statement from the given options regarding vertebrates, chordates, and invertebrates, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Understanding Chordates**:
- Chordates are a phylum that includes all animals with a notochord at some stage of their development. This phylum is divided into three subphyla: Urochordata (urochordates), Cephalochordata (cephalochordates), and Vertebrata (vertebrates).

**Hint**: Remember that chordates are characterized by the presence of a notochord.

2. **Analyzing the First Statement**:
- "All vertebrates are chordates."
- This statement is true because vertebrates are a subphylum of chordates. All vertebrates possess a vertebral column, which is a defining feature of this group.

**Hint**: Think about the hierarchy of biological classification and where vertebrates fit within chordates.

3. **Analyzing the Second Statement**:
- "All chordates are vertebrates."
- This statement is false. While all vertebrates are chordates, not all chordates are vertebrates. Urochordates and cephalochordates are examples of chordates that are not vertebrates.

**Hint**: Consider the examples of chordates that do not have a vertebral column.

4. **Analyzing the Third Statement**:
- "All invertebrates are chordates."
- This statement is also false. Invertebrates, by definition, do not have a backbone or notochord, which means they cannot be classified as chordates.

**Hint**: Recall the definition of invertebrates and their characteristics.

5. **Analyzing the Fourth Statement**:
- "All protochordates are vertebrates."
- This statement is incorrect. Protochordates, which include urochordates and cephalochordates, do not have a vertebral column and thus are not classified as vertebrates.

**Hint**: Remember the distinction between protochordates and vertebrates.

6. **Conclusion**:
- After analyzing all the statements, the only correct statement is "All vertebrates are chordates." Therefore, the correct answer is **Option A**.

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