Which one of the following does not have an open circulatory system?

Options

A. Chelone
B. Cockroach
C. Frog's tadpole
D. Both(1)and(3)

Answer

To determine which organism does not have an open circulatory system, we need to analyze the circulatory systems of the given options: Chelon (green sea turtle), Cockroach, Frog, and Stetopor.

### Step-by-Step Solution:

1. **Understand the Types of Circulatory Systems**:
- There are two main types of circulatory systems: open and closed.
- In an **open circulatory system**, blood is pumped into a body cavity (hemocoel) and is in direct contact with tissues. It is not contained in blood vessels.
- In a **closed circulatory system**, blood is contained within vessels (arteries, veins, and capillaries) and does not directly contact the tissues.

2. **Analyze Each Option**:
- **Chelon (Green Sea Turtle)**:
- Turtles are reptiles and belong to the vertebrate group. All vertebrates have a closed circulatory system. Therefore, Chelon has a closed circulatory system.
- **Cockroach**:
- Cockroaches are insects and belong to the invertebrate group. Insects have an open circulatory system. Therefore, the cockroach has an open circulatory system.
- **Frog**:
- Frogs are amphibians and also belong to the vertebrate group. Like all vertebrates, frogs have a closed circulatory system. Therefore, the frog has a closed circulatory system.
- **Stetopor**:
- This option is not commonly known, but if we assume it refers to a type of organism that is not a vertebrate, it may have an open circulatory system. However, without specific information, we cannot definitively categorize it.

3. **Conclusion**:
- From the analysis, both Chelon (green sea turtle) and Frog have a closed circulatory system.
- The only organism listed that has an open circulatory system is the Cockroach.
- Therefore, the organisms that do not have an open circulatory system are Chelon and Frog.

4. **Final Answer**:
- The correct answer is **both 1 (Chelon) and 3 (Frog)** do not have an open circulatory system.