It would be A. Today, Japan is a big ally.
The fall of the Mongols and the fall of the Byzantine Empire which led to decrease in trade. Hope this helps :)
Because the us wanted to spread from the Atlantic to the pacific.
A. European nations competed for land, trade, and military power.
Explanation: Industrialization and the emergence of bigger and stronger nations had caused competition between each other. The German and Italian Empire were recently established, as for the British and French were old empires with vast amounts of colonies. Austria-Hungary was already unstable and threatened small states in the Balkans which the Russian Empire backed them.