Diazo coupling is useful to prepare some :

Options

A. (a) pesticides
B. (b) dyes
C. (c) proteins
D. (d) vitamins

Explanation

**Step-by-Step Solution:**

1. **Understanding Diazo Coupling:**
- Diazo coupling is a chemical reaction where diazonium salts react with aromatic compounds to form azo compounds.
- Azo compounds are characterized by the presence of a functional group with the structure R-N=N-R', where R and R' are typically aromatic groups.

2. **Identifying the Products of Diazo Coupling:**
- The primary products of diazo coupling are colored azo compounds.
- These azo compounds are widely used in various applications, particularly in the dye industry.

3. **Analyzing the Options Given:**
- Option A: Pesticides - While some pesticides may contain azo compounds, diazo coupling is not primarily used for their synthesis.
- Option B: Dyes - This is the most relevant option, as diazo coupling is specifically known for producing azo dyes.
- Option C: Proteins - Proteins are biological macromolecules and are not synthesized through diazo coupling.
- Option D: Vitamins - Similar to proteins, vitamins are organic compounds that do not involve diazo coupling in their synthesis.

4. **Conclusion:**
- Based on the understanding of diazo coupling and its applications, the correct answer to the question is **Option B: Dyes**.