What does the word “maxim” (li.3) mean?

maxim is a short, pithy statement expressing a general truth

room is a really good movie.

answer is b.

  it is always the best policy to have good communication and good relations between individuals and, specially, between leaders of the countries. for this purpose, among others, there is a common place, the united nations, where the representants can present his and learn about the other country's policies.