I think the answer would be the third option.
Answer:
He uses this secondary purpose to help support the primary purpose: to persuade readers that a conquering prince must destroy a former republic if he hopes to hold it.
Explanation:
When I was alive I was keeping up with my oldest sister who used to threaten me and my other sister lol... during that time there was also politics going around and fires and plane crashes. Ofc I was only born in 2008 so..