why did it took several centuries before the civilizations of the two hemispheres had communication??

Due to lack of technology.

Explanation:

It took several centuries before the civilizations of the two hemispheres had communication because of lack of technologies that can make a bridge of communication between two hemisphere. People are not interested in research and having old wrong beliefs that prevent them from growth and development but due to renaissance movement people get rid of false and wrong beliefs and work for the advancement of technology which leads to communication between two hemisphere.

hello,

answer: a federal government has final authority on interstate/inter provincial  and international affairs, a confederation is one where the central/national government or authority is governing body what does not have final say over the same matters. hopefully this and i will try again if you don't like this answer : )

best of luck!

the first question's answer is a.