Open type of circulatory system is the system in which blood is pumped out of the heart and the cells and tissues are directly bathed in it. This type of circulatory system is found in :-

Options

A. Arthropoda, mollusca
B. Annelida, arthropoda, mollusca
C. Arthropoda, mollusca, cephalopod mollusca
D. Annelida, mollusca, cephalopod mollusca

Answer

To answer the question regarding the open type of circulatory system, we can break down the solution step by step:

### Step-by-Step Solution:

1. **Understanding the Open Circulatory System**:
- An open circulatory system is one where blood is not confined to vessels. Instead, it is pumped out of the heart and bathes the organs and tissues directly. This is in contrast to a closed circulatory system, where blood is contained within vessels.

2. **Identifying Organisms with Open Circulatory Systems**:
- Organisms that typically possess an open circulatory system include members of the phyla **Arthropoda** (e.g., insects, spiders, and crustaceans) and **Mollusca** (e.g., snails, clams, and octopuses).

3. **Evaluating the Options**:
- **Option 1**: Arthropoda and Mollusca – This option is correct because both of these groups have an open circulatory system.
- **Option 2**: Annelida, Arthropoda, and Mollusca – This option is incorrect because Annelids (e.g., earthworms) have a closed circulatory system.
- **Option 3**: Arthropoda, Mollusca, and Cephalopoda – This option is also incorrect because while Arthropoda and Mollusca have an open circulatory system, Cephalopoda (like squids and octopuses) have a closed circulatory system.
- **Option 4**: Annelida, Mollusca, Cephalopoda, and Mollusca – This option is incorrect for the same reasons as above; Annelida and Cephalopoda do not have an open circulatory system.

4. **Conclusion**:
- The correct answer to the question is that the open type of circulatory system is found in **Arthropoda and Mollusca**.

### Final Answer:
The open type of circulatory system is found in **Arthropoda and Mollusca**.