Parasitic animals have well-developed

Options

A. (a) digestive system
B. (b) reproductive system
C. (c) respiratory system
D. (d) all of the above

Answer

**Step-by-Step Solution:**

1. **Understanding Parasitic Animals**: Parasitic animals are organisms that depend entirely on a host for their survival. They derive nutrients and other necessities from the host, which is often harmed in the process.

2. **Identifying Relevant Animal Groups**: Parasitic animals are primarily found in certain groups within the animal kingdom, notably the phyla Platyhelminthes (flatworms) and Nematoda (roundworms).

3. **Analyzing the Digestive System**: Many parasitic animals do not have a well-developed digestive system. Instead, they absorb nutrients directly from their host through a specialized outer layer called tegument. Therefore, they do not possess a traditional digestive system.

4. **Examining the Reproductive System**: Parasitic animals have a well-developed reproductive system. This is crucial for their survival as they often reproduce in large quantities to increase the chances of their offspring surviving in the host environment.

5. **Considering the Respiratory System**: Parasitic animals typically do not have a complex respiratory system. They often respire through their skin or tegument rather than having specialized organs like lungs.

6. **Conclusion**: Based on the analysis of the systems present in parasitic animals, the well-developed system among the options provided is the reproductive system.

**Final Answer**: The correct answer is the reproductive system.

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