Which is true ?

Options

A. Chordates have ventral hollow nerve cord
B. All vertebrates have open circulatory system
C. All chordates are vertebrates
D. All vertebrates are chordates

Answer

To determine which statement is true regarding the classifications within the phylum Chordata, we will analyze each statement step by step.

### Step 1: Analyze the first statement
**Statement:** "Caudates have ventral hollow nerve cord."
- **Analysis:** This statement is incorrect. In the phylum Chordata, members of the subphylum Vertebrata have a dorsal hollow nerve cord, not a ventral one.

### Step 2: Analyze the second statement
**Statement:** "All vertebrates have an open circulatory system."
- **Analysis:** This statement is also incorrect. Vertebrates possess a closed circulatory system, which is more efficient than an open circulatory system found in some invertebrates.

### Step 3: Analyze the third statement
**Statement:** "All caudates are vertebrates."
- **Analysis:** This statement is incorrect. Caudata refers to a class within the phylum Chordata that includes amphibians like salamanders and newts, but not all members of the phylum are vertebrates. For example, cephalochordates and urochordates are also part of Chordata but are not classified as vertebrates.

### Step 4: Analyze the fourth statement
**Statement:** "All vertebrates are caudates."
- **Analysis:** This statement is correct. All vertebrates belong to the subphylum Vertebrata, which is a part of the phylum Chordata. Therefore, it can be concluded that all vertebrates are indeed caudates.

### Conclusion
Based on the analysis of each statement, the only true statement is:
**"All vertebrates are caudates."**

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