The enteronephric nephridia of earthworm are mainly concerned with

Answer

### Step-by-Step Solution:

1. **Understanding Enteronephric Nephridia**:
- Enteronephric nephridia are a type of excretory structure found in earthworms. They are responsible for the removal of waste products from the body.

2. **Types of Nephridia**:
- There are two main types of nephridia in earthworms: pharyngeal nephridia and septal nephridia. Both of these types are classified as enteronephric nephridia.

3. **Function of Enteronephric Nephridia**:
- The primary function of enteronephric nephridia is to excrete nitrogenous waste. This is crucial for maintaining the internal environment of the earthworm.

4. **Excretion Process**:
- The nitrogenous wastes are excreted into the alimentary canal. The alimentary canal is also referred to as the enteron.

5. **Conclusion**:
- Therefore, the enteronephric nephridia of earthworms are mainly concerned with the excretion of nitrogenous waste into the alimentary canal.