"The Prince" by Niccolò Machiavelli had a significant influence on European rulers in several ways. The most relevant response among the options you provided is:
It made rulers and their counselors think less about abstract ideals and more about actual human conduct and likely results.
Machiavelli's work emphasized practical governance over idealism, advocating for strategies that prioritized the effective exercise of power, often through pragmatic and sometimes ruthless means. While it may have encouraged some rulers to adopt trickery and cruelty, the broader impact was a shift towards a more realistic and sometimes cynical approach to leadership and statecraft, focusing on the realities of political power rather than abstract morals.