Which of these ideologies contributed powerfully toward the outbreak of world war i, especially in regions like the balkan peninsula?

The ideology of nationalism became very powerful in the Balkan peninsula wherein the people of the region believed that they had to isolate themselves from the presence of foreigners. Due to this attitude, there was tension that brewed between the Balkan region and the other countries. This eventually became one of the reasons for WWI. 

The answer to the question is a.