Final answer:
The best summary for the main idea of the passage from chapter 5 of The Prince is that former republics require tight control to prevent rebellion, as they are more difficult to govern than hereditary states.
Step-by-step explanation:
The option that best states the main idea of the passage from chapter 5 of The Prince is: Former republics are more difficult to rule than hereditary states, and they will rebel if they are not tightly controlled. This statement encapsulates Machiavelli's view that a new prince must understand the unique challenges that come with ruling a republic, specifically that such states have memories of their past autonomy and are prone to revolt if their affairs are not managed with a firm, controlling hand.