A sedentary sea anemone gets attached to the shell lining of hermit crab. The association is

Options

A. Commensalism
B. Amensalism
C. Ectoparasitism
D. Symbiosis

Explanation

To solve the question regarding the association between a sedentary sea anemone and a hermit crab, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Organisms Involved**:
- The two organisms in question are the sedentary sea anemone and the hermit crab.

2. **Understand the Nature of Their Association**:
- The sea anemone attaches itself to the shell lining of the hermit crab. This suggests a close physical relationship between the two organisms.

3. **Analyze the Benefits**:
- The sea anemone benefits by utilizing the nutrients available in the hermit crab's shell.
- The hermit crab may gain some camouflage from the sea anemone, which could help it avoid predators, but it is not directly benefiting from the anemone's presence in a significant way.

4. **Define the Type of Relationship**:
- In this scenario, the sea anemone is benefiting while the hermit crab is neither significantly helped nor harmed. This type of relationship is characterized as **commensalism**.

5. **Eliminate Other Options**:
- **Amensalism**: This involves one organism benefiting while the other is harmed, which is not the case here.
- **Ectoparasitism**: This involves one organism living on another and harming it, which does not apply here as the sea anemone does not harm the hermit crab.
- **Symbiosis**: This implies a mutual relationship where both organisms benefit, which is not the case here since the hermit crab does not derive significant benefits.

6. **Conclusion**:
- Based on the analysis, the correct answer is **commensalism**.

### Final Answer:
The association between the sedentary sea anemone and the hermit crab is **commensalism**.

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