One of the following is a connecting link between protozoans and poriferans

Options

A. cliona
B. leucosolenia
C. oscarella
D. proterospongia

Explanation

To solve the question regarding the connecting link between protozoans and poriferans, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Terms**:
- **Protozoans**: These are simple, single-celled organisms that belong to the kingdom Protista. They are considered primitive and are often referred to as the first forms of life.
- **Poriferans**: Commonly known as sponges, these are multicellular organisms that belong to the phylum Porifera. They are characterized by a porous body and are the simplest form of multicellular animals.

2. **Identify the Options**:
- The options provided are:
- Selenal
- Liposolenia
- Oscarella
- Pterospongia

3. **Analyze the Options**:
- To find the connecting link, we need to look for an organism that exhibits characteristics of both protozoans and poriferans.
- **Pterospongia** is known to be a colonial protozoan, which means it forms colonies similar to how sponges are structured.
- It possesses **choanocytes** (collar cells), which are also found in sponges. These cells are crucial for feeding and water flow in sponges.

4. **Conclusion**:
- Since Pterospongia has characteristics of both protozoans (being a colonial organism) and poriferans (having choanocytes), it serves as a connecting link between the two groups.
- Therefore, the correct answer is **Pterospongia** (Option 4).

### Final Answer:
The connecting link between protozoans and poriferans is **Pterospongia**.

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