A primary source is better than a secondary source because you know that it is absolutely true and that all aspects of the source are true.
the amount the other candidate pays for their campaign? if thats not what your asking we can talk in the comments.
Answer is C......................
The real causes of World War I included politics, secret alliances, imperialism, and nationalistic pride. However, there was one single event, the assassination of Archduke Ferdinand of Austria, which started a chain of events leading to war.
