To solve the question of which set of animals are triploblastic, true coelomates with an open type circulatory system, we can follow these steps:
### Step 1: Understand the terms
- **Triploblastic**: Animals that have three germ layers: ectoderm, mesoderm, and endoderm.
- **True Coelomates**: Animals that have a body cavity completely lined by mesodermal tissue.
- **Open Type Circulatory System**: A system where blood is pumped by the heart into open spaces (sinuses) rather than through vessels.
### Step 2: Identify the phyla
- **Triploblastic animals** include members from phyla such as Platyhelminthes, Annelida, Arthropoda, Mollusca, Echinodermata, and Chordata.
- **True coelomates** include members from phyla such as Annelida, Arthropoda, Mollusca, Echinodermata, and Chordata.
- **Open type circulatory system** is found in phyla such as Arthropoda and Mollusca.
### Step 3: Analyze the options
1. **Earthworm**:
- Phylum: Annelida
- Circulatory system: Closed
- Not a valid option.
2. **Cockroach, Octopus, and Leech**:
- Cockroach: Arthropoda (Open circulatory system)
- Octopus: Mollusca (Open circulatory system)
- Leech: Annelida (Closed circulatory system)
- Not a valid option due to leech.
3. **Mosquito, Ferritima, and Neris**:
- Mosquito: Arthropoda (Open circulatory system)
- Ferritima: Annelida (Closed circulatory system)
- Neris: Annelida (Closed circulatory system)
- Not a valid option due to Ferritima and Neris.
4. **Cockroach, Mosquito, and Pila**:
- Cockroach: Arthropoda (Open circulatory system)
- Mosquito: Arthropoda (Open circulatory system)
- Pila: Mollusca (Open circulatory system)
- All are triploblastic, true coelomates, and have an open type circulatory system.
### Step 4: Conclusion
Based on the analysis, the correct answer is option 4: **Cockroach, Mosquito, and Pila**.
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