Answer:
The most important contributions is that the Byzantium Empire was able to preserve a lot of the knowledge and culture from the Roman and Greek Empires.
The purpose of the Declaration of Independence is to explain to foreign nations and King George III why the colonies had chosen to separate themselves from Great Britain and become independent.
The introductory sentence states the Declaration's main purpose, to explain the colonists' right to revolution. In other words, “to declare the causes which impel them to the separation.” Congress had to prove the legitimacy of its cause. It had just defied the most powerful nation on Earth.