All of the countries were having a battle of who could build the biggest bombs, guns, tanks, weapons, technology, etc. which created tension between rival countries. everyone was afraid of the next country being too powerful. Hope it makes sense :-)
B and C. These are both benefits, the other two just don't have anything to do with what the question is asking.
Explanation:
charlemagne United his empire through reforms
A linkage institution<span> is a structure within a society that connects the people to the government or centralized authority. These institutions include: elections, political parties, interest groups, and the media.</span>
