Mark the incorrect option.

Options

A. The larva of Scoliodon exists.
B. Lateral line is absent in Bangarus.
C. Air bladder is present in Betta.
D. All chordates are deuterostomes.

Answer

To solve the question "Mark the incorrect option," we will analyze each of the provided options step by step to identify which one is incorrect.

### Step-by-Step Solution:

1. **Option 1: The larva of Ascoliodon exists.**
- Ascoliodon is a type of cartilaginous fish. Cartilaginous fishes, such as sharks and rays, are known for being viviparous, which means they give birth to live young rather than laying eggs. Additionally, fertilization occurs internally in these species. Since there is no larval stage in their development, this statement is incorrect.

2. **Option 2: Lateral line is absent in Bangaroos.**
- Bangaroos, commonly known as kraits, are snakes and belong to the class Reptilia. The lateral line system is primarily found in aquatic organisms, particularly fish, and is absent in terrestrial reptiles. Therefore, this statement is true.

3. **Option 3: Air bladder is present in Betta.**
- Betta fish are bony fish (Osteichthyes) and possess an air bladder (swim bladder), which helps them maintain buoyancy in the water. This statement is true.

4. **Option 4: All chordates are deuterostomes.**
- Chordates, along with Echinodermata and Hemichordata, are classified as deuterostomes. In deuterostomes, the blastopore develops into the anus during embryonic development. Thus, this statement is also true.

### Conclusion:
Based on the analysis, the incorrect option is **Option 1: The larva of Ascoliodon exists.**

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