Select the correct statement from the following .

Options

A. All vertebrates are chordates .
B. All protochordates are craniates.
C. All echinoderms are freshwater animals.
D. Post - anal tail is always present in chordates.

Answer

To solve the question "Select the correct statement from the following," we will analyze each of the provided statements one by one.

### Step 1: Analyze the First Statement
**Statement**: All vertebrates are chordates.
**Analysis**: This statement is correct. The phylum Chordata includes a subphylum called Vertebrata, which comprises all vertebrates. Therefore, every vertebrate is indeed a chordate.

### Step 2: Analyze the Second Statement
**Statement**: All protostomes are craniates.
**Analysis**: This statement is incorrect. While all vertebrates (which are a subset of chordates) are craniates, not all protostomes are craniates. Protostomes include a diverse group of animals that do not necessarily have a cranium.

### Step 3: Analyze the Third Statement
**Statement**: All echinoderms are freshwater animals.
**Analysis**: This statement is incorrect. Echinoderms are primarily marine organisms. They are not found in freshwater environments, making this statement false.

### Step 4: Analyze the Fourth Statement
**Statement**: Post-anal tail is always present in chordates.
**Analysis**: This statement is also incorrect. The post-anal tail is a characteristic feature of vertebrates, but some chordates, like certain tunicates, do not possess a post-anal tail in their adult form.

### Conclusion
After analyzing all the statements, we find that the only correct statement is the first one: **"All vertebrates are chordates."** Therefore, the correct answer is option A.

---