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 1: Identify the Options
The options provided are:
1. Trifolium
2. Indigo
3. Ferra
4. Lupine
5. Cassia

### Step 2: Analyze Each Option
- **Trifolium**: This plant is primarily used as fodder for livestock and does not produce blue dye.
- **Indigo**: This refers to the plant Indigofera, which is known for producing indigo dye.
- **Ferra**: This is likely a reference to Indigofera tinctoria, which is also used for dye extraction.
- **Lupine**: This is an ornamental plant and does not produce blue dye.
- **Cassia**: This is a shrub that is often grown ornamentally and does not produce blue dye.

### Step 3: Conclusion
From the analysis, both Indigo (Indigofera) and Ferra (Indigofera tinctoria) are known for producing blue dye. Therefore, the correct answer is **Indigo**.

### Final Answer
The plant used to extract the blue dye is **Indigo**.

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