Which is the respiratory organ of earthworm ?

Explanation

### Step-by-Step Solution:

1. **Identify the Organism**: The question asks about the respiratory organ of the earthworm. Earthworms belong to the phylum Annelida.

2. **Understand the Respiratory System**: In many organisms, there are specialized organs for respiration (like lungs in humans or gills in fish). However, earthworms do not possess any specialized respiratory organs.

3. **Recognize the Method of Respiration**: Earthworms respire through their skin. This type of respiration is known as cutaneous respiration.

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