Which of the following is an azo dye ?

Options

A. orange `-I`
B. Malachite green
C. Indigo
D. Martius yellow

Answer

To determine which of the given options is an azo dye, we need to understand the characteristics of azo dyes and analyze the structures of the provided options.

### Step-by-Step Solution:

1. **Understand Azo Dyes**:
- Azo dyes are organic compounds that contain one or more azo groups (-N=N-) in their structure. The presence of this functional group is what classifies a dye as an azo dye.

2. **Analyze Each Option**:
- **Option 1: Orange Dye**:
- The structure of orange dye contains an azo linkage (-N=N-). Therefore, it qualifies as an azo dye.
- **Option 2: Malachite Green**:
- The structure of malachite green does not contain an azo linkage. Thus, it is not an azo dye.
- **Option 3: Indigo Dye**:
- The structure of indigo dye also lacks an azo linkage. Therefore, it is not classified as an azo dye.
- **Option 4: Martius Yellow**:
- The structure of Martius yellow does not contain an azo linkage either. Hence, it is not an azo dye.

3. **Conclusion**:
- Based on the analysis, the only dye that contains the azo group (-N=N-) is the orange dye. Therefore, the correct answer is **Orange Dye**.

### Final Answer:
**Orange Dye** is an azo dye.