To solve this problem, let's analyze the reaction steps:$\newline$1. The starting compound is a diazonium salt, $(C_6H_5N_2^+Cl^-). \newline$2. The first step involves the reaction with $Cu_2Br_2/HBr. \newline$• This is a Sandmeyer reaction, where the diazonium group is replaced by a bromine atom.$\newline$• The product after this step is bromobenzene, $(C_6H_5Br). \newline$3. The second step involves the reaction with $Mg$ in dry ether.$\newline$• This forms a Grignard reagent, phenylmagnesium bromide, $(C_6H_5MgBr). \newline$4. The third step involves hydrolysis with water.$\newline$• The Grignard reagent reacts with water to form benzene, $(C_6H_6). \newline$Therefore, the final product is benzene, corresponding to Option 2.