The following is an example of Sandmeyer reaction

Options

A. `C_6H_5N_2^+Cl^(-)overset(CuCl//HCl)rarrC_6H_5Cl`
B. `C_6H_5N_2^+Cl^(-)overset(H_2"O"//Delta)rarrC_6H_5OH`
C. `C_6H_5N_2^+Cl^(-)overset(HBF_4)rarrC_6H_5F`
D. `C_6H_5N_2^+Cl^(-)overset(KI//"warm")rarrC_6H_5I`

Explanation

To determine which of the given reactions is an example of the Sandmeyer reaction, we need to understand the key components and conditions of the Sandmeyer reaction.

### Step-by-Step Solution:

1. **Identify the Sandmeyer Reaction**:
- The Sandmeyer reaction involves the conversion of an aryl diazonium salt into a haloarene (chlorobenzene or bromobenzene) using cuprous halides (CuX) in the presence of hydrogen halide (HX).

2. **Analyze the Given Options**:
- **Option A**: Benzene diazonium chloride reacts with CuCl and HCl to form chlorobenzene.
- **Option B**: Benzene diazonium chloride reacts with water and heat to form phenol.
- **Option C**: Benzene diazonium chloride reacts with HBF4 to form fluorobenzene.
- **Option D**: Benzene diazonium chloride reacts with potassium iodide to form iodobenzene.

3. **Evaluate Each Option**:
- **Option A**: This matches the Sandmeyer reaction criteria (CuCl + HCl). Therefore, this is a Sandmeyer reaction.
- **Option B**: This involves hydrolysis of the diazonium salt to form phenol, which is not a Sandmeyer reaction.
- **Option C**: This uses HBF4 to produce fluorobenzene, which is not part of the Sandmeyer reaction (only Cl and Br are formed).
- **Option D**: This uses potassium iodide to produce iodobenzene, which again does not fit the Sandmeyer criteria.

4. **Conclusion**:
- The only option that represents a Sandmeyer reaction is **Option A**, where benzene diazonium chloride reacts with CuCl and HCl to yield chlorobenzene.

### Final Answer:
**Option A** is the example of the Sandmeyer reaction.