Which of the following plants is used to extract the blue dye ?

Options

A. Trifolium
B. Indigofera
C. Lupin
D. Cassia

Explanation

To determine which plant is used to extract blue dye, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Options**: The options given are Trifolium, Indigo, Ferra, Lupine, and Cassia.

2. **Understand the Context**: The question specifically asks for a plant that is known for producing a blue dye.

3. **Research the Plants**:
- **Trifolium**: Commonly known as clover, not known for blue dye.
- **Indigo**: This refers to indigo dye, which is derived from certain plants.
- **Ferra**: Not commonly associated with blue dye.
- **Lupine**: Primarily known for its flowers and not for dye extraction.
- **Cassia**: Known for its medicinal properties and not for blue dye.

4. **Focus on Indigo**: The term "indigo" is directly associated with blue dye. The primary plants that produce indigo dye are from the genus **Indigofera**.

5. **Identify Specific Species**: The specific species known for blue dye extraction are:
- **Indigofera tinctoria**
- **Indigofera suffruticosa**

6. **Conclusion**: Based on the information, the correct answer is **Indigo**, specifically from the Indigofera genus.

### Final Answer:
The plant used to extract the blue dye is **Indigo** (from the genus Indigofera).

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