Which of the following statement is correct about the circulatory system of Annelida?

Options

A. Blood contains a respiratory pigment haemocyanin
B. Blood contains respiratory pigment haemoglobin in RBC
C. The have open type of circulatory system
D. The resipiratory pigment is haemoglobin dissolved in plasma

Answer

To determine the correct statement about the circulatory system of Annelida, let's analyze the provided options step by step.

### Step-by-Step Solution:

1. **Understanding the Circulatory System of Annelida**:
- Annelids, such as earthworms, have a closed circulatory system. This means that their blood is contained within vessels and does not flow freely in the body cavity.

2. **Evaluating the Statements**:
- **Statement 1**: "Blood contains respiratory pigment of hemocyanin."
- This statement is incorrect. Hemocyanin is a respiratory pigment found in some arthropods and mollusks, not in Annelida. Annelids have hemoglobin as their respiratory pigment.

- **Statement 2**: "Blood contains respiratory pigment hemoglobin and RBC."
- This statement is also incorrect. While Annelids do have hemoglobin, it is not present in red blood cells (RBCs) as in vertebrates. Instead, hemoglobin is dissolved in the plasma of their blood.

- **Statement 3**: "They have an open type of circulatory system."
- This statement is incorrect. Annelids possess a closed circulatory system, not an open one.

- **Statement 4**: "The respiratory pigment is hemoglobin dissolved in plasma."
- This statement is correct. In Annelida, hemoglobin is indeed dissolved in the plasma and serves as the respiratory pigment.

3. **Conclusion**:
- The correct statement about the circulatory system of Annelida is: "The respiratory pigment is hemoglobin dissolved in plasma."

### Final Answer:
The correct statement about the circulatory system of Annelida is: **The respiratory pigment is hemoglobin dissolved in plasma.**