All the reactions given as choices , and are different methods of preparation of ethoxyethane but only the following is called Williamson synthesis. Williamson synthesis sod.ethoxideC2H5ONa+EthylbromideC2H5Br EthoxyethaneC2H5−O−C2H5+NaBr C2H5OHAl2O3C2H5OC2H5 C2H5OHH2So4Δ430−440C2H5OC2H5 C2H5OHAg2OC2H5OC2H5
Above , and are the methods of preparing ethoxy ethane but not the Williamson's synthesis method.