Which one of the following is a protochordate

Options

A. Amphioxus
B. Lamprey
C. Labeo
D. Exocoetus

Answer

To determine which of the following is a protochordate, we need to analyze the options provided: amphioxus, lamprey, labio, and exocetus.

### Step-by-Step Solution:

1. **Identify the Options**: The options given are:
- A) Amphioxus
- B) Lamprey
- C) Labio
- D) Exocetus

2. **Understand Protochordates**: Protochordates are the earliest forms of chordates and include groups such as cephalocordates and urochordates. They are characterized by having a notochord, dorsal nerve cord, and pharyngeal slits at some stage of their life cycle.

3. **Analyze Each Option**:
- **A) Amphioxus**: This organism belongs to the group Cephalocordata, which is a type of protochordate. Therefore, amphioxus is a protochordate.
- **B) Lamprey**: Lampreys belong to the class Cyclostomata, which are jawless fish and classified as true chordates (eukordates), not protochordates.
- **C) Labio**: Labio (also known as Labeo) is a genus of freshwater fish, which are also classified as eukordates.
- **D) Exocetus**: Exocetus, commonly known as flying fish, also belong to the eukordates.

4. **Conclusion**: Based on the classification, the only organism from the options that qualifies as a protochordate is **Amphioxus**.

### Final Answer:
**A) Amphioxus** is the protochordate among the given options.

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