Answer:
The assasination of Archduke Franz and the alliance system ARE A MAJOR CAUSE.
Step-by-step explanation:
The alliance system was when of course everyone had an ally. When Archduke Franz was assinated nations started ordering and asking for their alliances help. Alliance to alliance and so on. Eventually it became WWI. THESE ARE MAJOR CAUSES
AVOID THEM. However, by process of elimination should help you find your answer and cancel out these two.