How does the Islamic world advance culture and science?

i think the answer is b.

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.

collect the tariff by force if necessary

use the military to enforce a federal law

b and c