Guano is

Options

A. a kind of down feather
B. a flightless bird
C. faecal matter of sea birds, used as fertilizer
D. a fastest flying bird.

Answer

**Step-by-Step Solution:**

1. **Understanding Guano**: Guano is defined as the excrement (fecal matter) of seabirds. It is important to note that it specifically refers to the droppings of birds that live in marine environments.

2. **Composition of Guano**: The fecal matter of seabirds is rich in essential nutrients, particularly nitrogen, phosphorus, and potassium. These nutrients are crucial for plant growth and development.

3. **Uses of Guano**: Due to its high nutrient content, guano is commonly used as a manure and fertilizer in agriculture. It helps improve soil fertility and promotes healthy plant growth.

4. **Evaluating Options**: When presented with multiple-choice options regarding what guano is, we can eliminate the incorrect options:
- A kind of down feather: Incorrect, as down feathers are soft feathers used for insulation, not excrement.
- A flightless bird: Incorrect, as guano is not a type of bird but rather the waste produced by birds.
- Fecal matter of seabirds used as fertilizer: Correct, as this accurately describes guano.
- A fastest flying bird: Incorrect, as this does not relate to the definition of guano.

5. **Conclusion**: The correct answer is that guano is the fecal matter of seabirds used as fertilizer.

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