Which one of the following has an open circulartory system

Options

A. Octopus
B. Pheretima
C. Periplaneta
D. Hirudinaria

Answer

To determine which of the following organisms has an open circulatory system, we need to analyze each option provided:

1. **Understanding Circulatory Systems**:
- **Open Circulatory System**: Blood is not always contained within vessels; it flows freely through cavities (hemocoel) and directly bathes the organs. This system is commonly found in arthropods and some mollusks.
- **Closed Circulatory System**: Blood is contained within vessels, and it circulates through a network of arteries, veins, and capillaries. This system is found in vertebrates and some invertebrates like annelids.

2. **Analyzing Each Option**:
- **A. Octopus**: Octopuses belong to the phylum Mollusca and have a closed circulatory system. Therefore, this option is incorrect.
- **B. Ferritima**: This organism belongs to the phylum Platyhelminthes (flatworms), which also have a closed circulatory system. Thus, this option is incorrect.
- **C. Periplaneta**: This is the scientific name for the American cockroach, which belongs to the phylum Arthropoda. Arthropods are known to have an open circulatory system. Therefore, this option is correct.
- **D. Herudinaria**: This organism belongs to the phylum Annelida (segmented worms) and has a closed circulatory system. Hence, this option is incorrect.

3. **Conclusion**:
- Based on the analysis, the organism that has an open circulatory system is **C. Periplaneta** (the cockroach).

### Final Answer:
The organism with an open circulatory system is **C. Periplaneta**.