Closed circulatory system is found in-

Options

A. Arthopod and chordates
B. Molluscs and chordates
C. Amphibians and molluscs
D. Annelids and chordates

Answer

**Step-by-Step Solution:**

1. **Understanding the Closed Circulatory System**: A closed circulatory system is one where the blood is contained within blood vessels, allowing for more efficient transport of nutrients and oxygen to tissues.

2. **Identifying Organisms with Closed Circulatory Systems**:
- **Annelids**: All annelids (like earthworms) have a closed circulatory system.
- **Cephalopods**: Some mollusks, particularly cephalopods (like octopuses and squids), also possess a closed circulatory system.
- **Vertebrates**: All vertebrates (including mammals, birds, reptiles, amphibians, and fish) have a closed circulatory system.

3. **Reviewing the Options**:
- **Option 1**: Arthropoda - They typically have an open circulatory system.
- **Option 2**: Mollusca - While some mollusks have a closed system (like cephalopods), most have an open circulatory system.
- **Option 3**: Annelida - This group has a closed circulatory system.
- **Option 4**: Cephalopoda - This subgroup of Mollusca has a closed circulatory system.

4. **Conclusion**: The correct answer is that a closed circulatory system is found in Cephalopoda (option 4).

**Final Answer**: Closed circulatory system is found in Cephalopoda.

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