Which reagent is used to convert benzene diazonium chloride to chlorobenzene?

Solution

1. The conversion of a diazonium salt to an aryl halide is known as the Sandmeyer reaction.
2. The standard reagents for this transformation are $\text{CuCl}$ and $\text{HCl}$.
3. This reaction effectively replaces the $-{\text{N}}_2^{+}{\text{Cl}}^{-}$ group with $-\text{Cl}$.
4. Hence the answer is (A).