The navigation act required them to trade
Spain felt that Portugal would dominate the world's trading routes and resources and it motivated them to compete with them and invest into their own campaigns, such as the one of Columbus.
B is the only one that sounds like it's not in the right question. Unless you know for sure it's not B, that's my suggestion.
Answer:
The Rhine and the Danube.
Explanation:
The rivers forming the north and east border of the Roman Empire are the Rhine and the Danube.
One way Diocletian brought short-term order to Rome was to "divide the empire" into to distinct spheres--in the hope that this would make it easier to manage.
