What are you specifically looking for in this answer?
Out of the choices given, the body of water that the Eastern Roman Empire bordered was the Black Sea. The capital of of the empire was Constantinople and it was the closest to the Black Sea. The correct answer is A.
The correct answer is D) a system in which states agree to form a national government, but maintain its sovereignty.
<em>A Confederation is a system in which states agree to form a national government but maintain its sovereignty.
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In political terms, a Confederation is considered a union of states but maintaining its own soverignty. The United States formed a Federation in 1789, to unify even more the states, something that other states did not like and mostly the Southern states maintained the concept of Confederation. The Federation was based on the idea of a common government for all the states, meanwhile, in a Confederation, the common element was the autonomy in each of the states.
A career I'd say that these qualifications would be most applicable would be the career of being a researcher.
Hope this helped! :)