In Physalia, the float is

Options

A. Crimson
B. Brown
C. Blue
D. Colourless.

Answer

### Step-by-Step Solution:

1. **Identify the Organism**: The question refers to Physalia, commonly known as the Portuguese man-of-war.

2. **Understand the Structure**: Physalia has a specialized structure called a pneumatophore, which is a gas-filled sac.

3. **Function of the Pneumatophore**: The pneumatophore acts as a float, allowing Physalia to stay buoyant on the surface of the water.

4. **Color of the Pneumatophore**: The pneumatophore is typically violet or purple in color, which is why Physalia is often referred to as having a blue appearance.

5. **Conclusion**: Therefore, the float in Physalia is a gas-filled pneumatophore that is purple to blue in color.

### Final Answer:
In Physalia, the float is a gas-filled pneumatophore that is purple to blue in color.

---