One achievement of Roman Empire was posting the Twelve Tablets. So the correct option for the given question is option "D".The twelve tablets were the twelve laws of the Roman Empire that were engraved in copper plates and displayed for the viewing of all people. These set of laws were created to bring all Roman citizens under a single set of rules. Laws like allowing death sentence was only possible by the law courts. It could not be given by any person randomly. No cremation or burials were allowed inside the walls of the city. Twelve such rules were needed to be followed by the citizens.