The correct answer is: C. Medieval philosophers believed a ruler should base his actions on Christian principles; Machiavelli argued that a ruler should do whatever is necessary to secure and unite his state.
This is described by Machiavelli in his animal imagery metaphor, which says that "A ruler must be a fox and a lion. A Lion to induce fear and get things done and a fox to manipulate and be sly".
In addition, Machiavelli said that a ruler should appear compassionate, honest and religious, even if he is not those things and try to do what is right. But, if he can not, he must put his morals aside and do what needs to be done.
Machiavelli's signature quote was "It is better to be feared than loved".
On the other hand, Medieval philosophers believed that a ruler should follow the right way, because a good ruler is a living likeness of God.