Which one of the following respires only through skin?

Options

A. Fish
B. Frog
C. Earthworm
D. Human

Answer

### Step-by-Step Solution:

1. **Understand the Question**: The question asks which organism respires only through the skin. This means we need to identify an organism that does not use any other method (like lungs or gills) for respiration.

2. **Evaluate the Options**:
- **Option A: Fish** - Fish primarily respire through gills, not skin. Therefore, this option is incorrect.
- **Option B: Frog** - Frogs can respire through both gills (when they are tadpoles) and lungs (as adults). Hence, this option is also incorrect.
- **Option C: Earthworm** - Earthworms do not have lungs. They live in soil and respire through their skin. This option is correct.
- **Option D: Humans** - Humans breathe through lungs, making this option incorrect.

3. **Identify the Correct Answer**: After evaluating all the options, the organism that only respires through the skin is the earthworm.

### Final Answer: Earthworm

---