Sepia and Octopus swim swiftly by means of

Options

A. Arms
B. Lateral fins
C. Suckers
D. Jet propulsion through siphon

Answer

To answer the question "Sepia and Octopus swim swiftly by means of," we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Organisms**: Recognize that both Sepia (cuttlefish) and Octopus belong to the class Cephalopoda within the phylum Mollusca.

2. **Understand the Swimming Mechanism**: Cephalopods, including Sepia and Octopus, have a unique method of swimming. They utilize a structure known as the mantle cavity.

3. **Function of the Mantle Cavity**: The mantle cavity can be filled with water. This is crucial for their swimming ability.

4. **Water Expulsion**: When the water is expelled from the mantle cavity, it is forced out through a funnel-like structure called the siphon.

5. **Direction of Movement**: The expulsion of water through the siphon propels the organism in the opposite direction, allowing for swift movement.

6. **Jet Propulsion**: This method of movement is referred to as jet propulsion, which is a key characteristic of cephalopods.

7. **Conclusion**: Therefore, the correct answer to the question is that Sepia and Octopus swim swiftly by means of jet propulsion.

### Final Answer:
Sepia and Octopus swim swiftly by means of jet propulsion.

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