The central idea of this text is that Adams and Jefferson's friendship might have been paused for a decade after the election, and even though they disagreed on several points, they still worked together to create a new nation. The third option is the right answer of part A.
The way the author uses details to express this idea is by describing Jefferson and Adams' disagreements as well as their common ground and affection for one another. The first option is the right answer for part B.
The friendship between Adams and Jefferson demonstrates that people with different views can still work together.
The author describes the disagreements between Adams and Jefferson, as well as the common ground the two men found and their affection for one another.
The author's main purpose in writing this passage is to show how Adams and Jefferson had different views and opinions, yet were able to not only cultivate a friendship but collaborate in government frequently. He believes this is an example of the kind of political discourse and action we need to foster in American politics. The way he provides evidence for this claim is by providing details as to the common ground between them, as well as their disagreements.