Typical nephridium of earthworm is 

Options

A. Closed enteronephric nephridium
B. Open exonephric nephridium
C. Open enteronephric nephridium
D. Closed exonephric nephridium

Answer

To determine the type of typical nephridium found in earthworms, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Nephridium**: Nephridia are excretory organs found in annelids, including earthworms. They play a crucial role in the elimination of waste products from the body.

2. **Identify the Types of Nephridia**: There are two main types of nephridia based on their structure and function:
- **Exonephric Nephridia**: These open to the outside of the body.
- **Entonephric Nephridia**: These open into a coelomic cavity.

3. **Focus on Earthworm Nephridia**: In earthworms, the typical nephridia are known as integumentary nephridia.

4. **Characteristics of Integumentary Nephridia**:
- They are small in size.
- They open directly to the exterior through a nephridial pore.
- They do not have a nephrostome (an opening leading into the nephridium) or a nephrotome (a segment of the nephridium).
- There is no connection to the coelomic cavity (no opening into the coelom).

5. **Classify the Type**: Given the characteristics:
- Since they open to the outside (exonephric) and do not connect to the coelom (closed), we classify them as **closed exonephric nephridia**.

6. **Select the Correct Option**: Based on the classification, the correct answer to the question is **closed exonephric nephridium**.

### Final Answer:
The typical nephridium of earthworm is **closed exonephric nephridium** (Option D).

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