Option D, by posting a well-trained army throughout the empire is the right answer.
The Roman army played a vital role in the Roman empire. With the help of army Roman emperors accomplished with conquering so many clans, tribes and confederations. This army was used to protect the territory of Rome, and also to control the conquered people. Roman soldiers fought with swords, knives and long spears. They were also provided with a shield for their protection. In this way, Roman Emperor managed to protect the territory of the conquered land.
