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 need to analyze each of the provided options to identify which one contains incorrect information.

### Step-by-Step Solution:

1. **Analyze Option 1: "The larva of Squalidon exists."**
- Squalidon refers to a genus of extinct marine mammals. The statement suggests that the larva of Squalidon exists, which is misleading as Squalidon is not known to have a larval stage. Therefore, this statement is incorrect.

2. **Analyze Option 2: "Lateral line is absent in Bangalore."**
- The lateral line system is a sensory organ found in many aquatic organisms that helps detect movement and pressure changes in the water. The statement claims that the lateral line is absent in Bangalore. This is a correct statement, as the lateral line is indeed absent in terrestrial organisms, including those in Bangalore. Thus, this option is correct.

3. **Analyze Option 3: "Ear bladder is present in beta."**
- The term "ear bladder" likely refers to the swim bladder, which is present in many fish, including Betta fish (often referred to as beta). This statement is correct, as Betta fish do possess a swim bladder.

4. **Analyze Option 4: "All caudates are deuterostomes."**
- Caudates (or Urochordates) are indeed classified as deuterostomes. This statement is also correct, as deuterostomes include echinoderms and chordates (which caudates fall under).

### Conclusion:
After analyzing all options, the incorrect option is **Option 1: "The larva of Squalidon exists."**