Chordates have

Options

A. Dorsal, hollow and single CNS
B. Ventral heart
C. Post-anal tail
D. All

Answer

To answer the question "Chordates have," we need to identify the key characteristics that define the phylum Chordata. Here’s a step-by-step breakdown:

### Step 1: Identify the Key Characteristics of Chordates
Chordates are defined by four primary characteristics that are present at some stage of their development. These are:

1. **Dorsal, Hollow Nerve Cord**: This is a central nervous system structure that runs along the back of the organism.

2. **Notochord**: A flexible rod-like structure that provides support. In many chordates, it is replaced by the vertebral column (spine) during development.

3. **Pharyngeal Slits**: These are openings in the pharynx that can develop into gill structures in aquatic species, aiding in respiration.

4. **Post-anal Tail**: An extension of the body that is located behind the anus, which is often used for locomotion.

### Step 2: Explanation of Each Characteristic
- **Dorsal, Hollow Nerve Cord**: This structure is crucial for the nervous system and is responsible for transmitting signals throughout the body.

- **Notochord**: It serves as a primitive backbone and is important for the development of the spinal column in vertebrates.

- **Pharyngeal Slits**: These slits are significant for respiration and can also play a role in feeding in some species.

- **Post-anal Tail**: This feature aids in movement and balance, especially in aquatic species.

### Step 3: Conclusion
Based on these characteristics, we can conclude that all these features are essential traits of chordates. Therefore, the answer to the question "Chordates have" is that they possess a dorsal, hollow nerve cord, a notochord, pharyngeal slits, and a post-anal tail.